You can make an outbound call using the following API with the help of a REST client.
The auth_id can be found in your dashboard: https://console.plivo.com/dashboard/
There are three mandatory requirements that must be met to make an outbound call.
The phone number to be used as the caller ID (with the country code). For example, a USA caller ID number would look like 15677654321, where '1' is the country code.
Use the regular number(s) or SIP endpoint(s) to make a call. Regular number must be prefixed with country code but without the + sign. For example, to dial a number in the USA, the number would look like 15677654321, where '1' is the country code.
SIP endpoints must be prefixed with SIP – for instance, sip: email@example.com.
This is the URL invoked by Plivo when the outbound call is answered.
To add additional options on the API, please refer to this guide: https://www.plivo.com/docs/api/call/#arguments