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  • What happens if a high-risk number is wrongly classified and affects my service?

    If you encounter a situation where a number is wrongly classified as high-risk, please contact our support team. We will conduct a thorough review and make necessary adjustments. We aim to minimize inconvenience and ensure your communication services run smoothly.

  • What measures does Plivo take to ensure the accuracy of its high-risk and premium number database?

    Our team regularly reviews and updates our database to reflect the latest high-risk and premium number information. This includes compliance with regulatory updates and integrating customer feedback and incident reports. We may collaborate with our carrier partners to clarify a specific prefix when necessary.

  • How does Plivo classify a number as 'high-risk' or 'premium'?

    Plivo uses a combination of industry-standard databases, historical call data, and ongoing analysis of calling patterns to classify numbers as high-risk or premium. We continuously monitor these sources to update our classifications and ensure the safety and security of our customers.

  • What if my use case requires calls to high-risk numbers?

    You can request activation of high-risk permissions for your account by contacting our support team and providing details of your use case. The validation process for disabling a premium prefix block for a specific account and use case can take 48 hours or longer. We make every effort to expedite this process.

  • What are premium or high-risk numbers?

    Premium or high-risk numbers are phone numbers that connect callers to special services, often carrying higher charges compared to regular calls. These additional charges, paid to the service provider, place premium-rate numbers at a greater risk of exploitation through traffic pumping. Traffic pumping is a form of telecom fraud where bad actors artificially inflate traffic to their premium-rate numbers. When conducted internationally, this form of toll fraud is known as International Revenue Share Fraud (IRSF).

    Plivo classifies numbers as premium or high-risk based on factors such as the associated rates, call patterns, susceptibility to toll fraud, and third-party trends.

    Most businesses never need to contact premium rate numbers; therefore, by default, Plivo blocks calls to all phone numbers with high-risk prefixes to prevent unwanted charges.

    Plivo has identified thousands of premium rate and high-risk prefixes. You can export a list of these prefixes in the Plivo console by navigating from Zentrunk > Geo Permissions > High-Risk Permissions. Plivo regularly updates this list based on factors such as the rates associated with the premium numbers, call patterns, and third-party trends.


  • Can I map Plivo numbers to inbound trunks using an API?

    Yes, you can map Plivo numbers to inbound trunks using the Account Phone Number API. Pass the api_id as the inbound trunk_id to map the number to an inbound trunk.

  • Origin-Based Pricing

    Plivo has introduced origin-based pricing on its Zentrunk and Voice API offering. Origin-based pricing is a concept where one destination has different call rates depending on where the call has originated from. As a result, Plivo customers benefit from reduced calling prices from specific origins, for select regions. 

    We will continue to expand our coverage into other destinations in line with our carrier partners.

    How will origin-based pricing benefit me?

    Historically, we did not differentiate call rates based on where the call originated from. Plivo has built in the routing intelligence to identify the call origin country and incorporate the corresponding rate. This means a single destination can have different call rates.
    For example, a call originating from a country outside of Europe toward Austria - Mobile numbers costs $0.3980, while a call originating from a European country toward Austria - Mobile numbers costs only $0.0390, or about one-tenth as much.

    Which countries have origin pricing applicable?

    Plivo offers origin-based pricing in Europe for calls that terminate in these countries:

    1. Austria
    2. Belgium
    3. France
    4. Germany
    5. Hungary
    6. Italy
    7. Netherlands
    8. Poland
    9. Portugal
    10. Spain

    Which countries qualify for origin-based pricing?

    Calls that originate from the following countries qualify for origin-based prices:
    Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, United Kingdom

  • Does Plivo support E.164 format calling?

    Yes, Plivo supports both inbound and outbound calls made using the E.164 format. If Plivo receives a request in a non-E.164 format, it will append a plus sign, followed by the country ISO code and the number in the SIP invite, then forward the call to the next leg.

    Any outbound calls made in a non-E.164 format will fail.

  • Does Zentrunk support SIP over TLS?

    Plivo Zentrunk supports SIP over TLS and media over SRTP.

  • What SIP request methods does Zentrunk SIP trunking support?

    Zentrunk supports these SIP methods: ACK, BYE, CANCEL, INVITE, OPTIONS, and UPDATE. We don’t support INFO, MESSAGE, NOTIFY, PRACK, PUBLISH, REFER, REGISTER, or SUBSCRIBE.

  • What methods of authentication does Zentrunk SIP trunks support?

    Zentrunk supports the following methods for authentication:

    1. IP access control list-based authentication
    2. Auth-based authentication with username and password
    3. Both methods used together
  • What is the calls per second (CPS) limitation for Zentrunk SIP trunking?

    Outbound Limitations

    The calls-per-second limitation for Zentrunk SIP trunking is based on both account-level CPS and trunk-level CPS. The account-level CPS is the rate at which calls may be made from an account in a second, while the trunk-level CPS applies to each of the trunks individually in the account. 

    Businesses can choose different ways to allocate their account-level CPS across trunks in their account.

    Scenario 1:

    A user has 25 account-level CPS and 3 trunks 

    • 2 trunks are set at 10 CPS (high-volume use cases)
    • 1 trunk is set at 5 CPS (low-volume use case)

    Scenario 2:

    A user has 10 account-level CPS and 10 trunks 

    • Each trunk has a CPS of 10
    • This allows for a “free-for-all” where if one trunk is consistently initiating calls at a rate of 10 CPS, calls from other trunks would fail

    Note: You cannot exceed the account CPS limit even if you have multiple trunks in your account. If it exceeds, then calls will fail with the error “cps_limit_reached” and error code “5180.”

    By default, the CPS for Zentrunk is set to two calls per second per account and one call per second per trunk. If you need higher CPS requirements, please contact our sales team. For help with technical issues related to Zentrunk, please submit a ticket with the Plivo support team.

    Inbound Limitations

    There are no calls-per-second constraints for inbound trunks in Zentrunk SIP trunking.

  • Can I record a call on Zentrunk?

    Zentrunk does not support call recording.

  • Will a Zentrunk SIP URI work with my softphone?

    Yes, you can use a Zentrunk SIP URI to make calls from any softphone. Create an account on your softphone, then uncheck "register with domain and receive calls" under the account preferences.

    Read our Zentrunk quickstart guide and interconnection guides for FreeSWITCH, Asterisk, FreePBX, 3CX, FusionPBX, and Twilio.


  • Do Zentrunk SIP trunks support SIP OPTIONS pings?

    Yes, Zentrunk SIP trunks support SIP OPTIONS pings. 

    SIP OPTIONS pings are widely used as a health check mechanism in SIP communications networks. You can have your PBX issue SIP OPTIONS messages as a ping mechanism to a Zentrunk SIP trunk and Zentrunk will respond with an appropriate response. 

    SIP OPTIONS are supported only on sending requests to an outbound trunk URI and not to trunk IP addresses.  We recommend not sending more than one SIP OPTIONS message every 10–15 seconds to avoid your requests getting blocked.


  • Is Plivo’s Zentrunk secure?

    Your calls securely connect with IP authentication and credential-based validation. Zentrunk offers Transport Layer Security (TLS) for signaling encryption and Secure Real-time Transport Protocol (SRTP) for media encryption.

  • How can I increase the capacity of my Zentrunk SIP trunk?

    Your calls per second (CPS) allowance defines the number of outbound calls you can initiate every second. By default, each account can initiate one call per second. Contact the Plivo sales team if you need a higher CPS limit for your account.  

    There are no limitations to the number of concurrent calls you can make using Zentrunk. Zentrunk servers are elastic in nature — they can scale up or down depending on call traffic. No additional configurations are required to add more capacity. 

    Zentrunk SIP trunks are charged on a pay-as-you-go basis; you're charged only for the minutes you use.

  • How many connectivity endpoints or points of presence does Plivo Zentrunk SIP trunking have?

    Plivo has seven connectivity endpoints or PoPs (points of presence) servers across five continents to ensure optimal voice quality and minimum latency:

    • North California, USA
    • Virginia, USA
    • Frankfurt, Germany
    • São Paulo, Brazil
    • Sydney, Australia
    • Singapore
    • Mumbai, India

    When a user initiates a call, Plivo locates the closest PoP to handle the call based on the source IP address. This reduces latency and delay in establishing calls.

  • Is there a limit to how many Zentrunk trunks and IP access control lists can I create?

    The recommended number of trunks per account is 100. There is no limit to the number of IP access control lists you can create with your Plivo account.

  • Does Plivo Zentrunk SIP trunking support T.38 fax?

    Unfortunately, no.

  • What codecs do Zentrunk SIP trunks support?

    Zentrunk SIP trunks support PCMA and PCMU codecs.

  • What DTMF types does Zentrunk SIP trunking support?

    Zentrunk SIP trunking supports RFC-2833.

  • What equipment do I need to be able to use Zentrunk SIP trunking?

    Zentrunk can work with any SIP-based device, such as an IP PBX or session border controller (SBC), or any softphone SIP client, such as Zoiper or X-Lite (Bria Solo Free). Refer to our Zentrunk Getting Started Guide for more information.

  • Why am I being charged for abandoned and short calls?

    Voice calls while using Plivo’s services are subject to carrier regulations within both the region where the call is made and the region where the call is received. Per our legal terms of service, the following conditions and surcharges apply:

    • Abandoned calls during any applicable calendar month should be less than 20%. Abandoned calls are defined as calls initiated by Plivo that are of zero seconds in duration, where the end user did not answer or rejected or missed the calls. If more than 20% of total call attempts are abandoned calls during any applicable calendar month, Plivo reserves the right to charge an abandoned call surcharge of $0.02 per call for abandoned calls in excess of that threshold. The percentage of abandoned calls is determined by dividing the total number of abandoned calls by the total number of calls.
    • Average call duration (ACD) during any applicable calendar month should be greater than 35 seconds. If the ACD during any applicable calendar month is less than 35 seconds, Plivo reserves the right to charge an ACD surcharge equal to the number of minutes the customer would have used if the ACD had equaled 35 seconds for the number of calls actually completed minus the number of minutes customer actually used for calls completed, multiplied by an ACD surcharge of $0.02 per minute.
    • Short duration calls during any calendar month should be less than 10%. Short duration calls are defined as calls initiated by Plivo and answered by the call recipient and that are less than 6 seconds in duration. If, during any calendar month, 10% or more of a customer’s completed calls are short duration calls, Plivo reserves the right to charge a surcharge of $0.015 per short duration call.
    • Incomplete calls to incoming toll-free numbers during any calendar month should be less than 5%. Incomplete calls are defined as calls received by Plivo on a toll-free number that are of zero seconds in duration, for which the Plivo customer who owns or rents the toll-free number has not answered or has rejected the calls. If more than 5% of total call attempts are incomplete toll-free calls during any calendar month, Plivo reserves the right to charge an incoming toll-free call surcharge of $0.10 per call on incomplete calls in excess of that threshold. The percentage of incomplete calls to incoming toll-free calls is determined by dividing the total number of incomplete toll-free calls by the total number of calls.

    Fee Disputes. If you wish to dispute fees associated with your account, please contact us through our support portal within 30 days of the date of the activity that generated the dispute. Refunds issued to resolve a dispute are issued as credits to your account and not as cash refunds. Disputes older than 90 days are not entitled to any refunds or credits.