Local phone numbers in the US and Canada follow a specific format. To understand this better we can take a look at an example phone number: 1415906XXXX. This number can be broken down in the following parts:
1 : Represents the Country dialing code
415 : Numbering plan area code of the phone number (NPA)
906 : Exchange code(NXX)
XXXX : Line number or Subscriber number
All local phone numbers in the US and Canada follow this notation: (1) NPA NXX <Line>
Each of these NPANXX combinations is assigned to a Rate Center. This Rate Center defines the boundaries of local calling and the subsequent billing. Calls between phone numbers belonging to the same Rate Center are considered as local calls and are subject to local calling rates whereas calls between different Rate Center might be subject to long-distance calling rates.
Some important points to note here:
Each Rate Center has multiple NPANXX combinations associated with it.
Each NPANXX is uniquely associated with one Rate center.
Single NPA might be mapped to multiple Rate Centers i.e. Using the numbers with the same NPA does not guarantee local calling rates.
We, at Plivo, try to provide a wide variety of phone numbers to our customers but cannot guarantee the availability of all NPANXXs. In such cases, please reach out to our support team for the best available solution. If requested NPANXX phone numbers are available with our carrier-partners, our support team will provide the same to you and we will also ensure the future availability of such numbers in our phone number inventory.
In cases, where our carrier partners are not able to provide the requested NPANXX, we will provide you phone numbers from the same rate center as the requested NPANXX, ensuring that your customers are charged local calling rates.