For starting a call you can just open the Reve SaaS Dashboard and from contacts page, you can place call.
But if you want to place call directly from your app, you need to use the following apis.
1. Placing a free audio call :
ReveSaaS.makeAudioCall(activity, numberToCallWithCountryCode);
Example
ReveSaaS.makeAudioCall(MainActivity.this, "+8801844097722");
2. Placing a free videocall :
ReveSaaS.makeVideoCall(activity, numberToCallWithCountryCode);
Example
ReveSaaS.makeVideoCall(MainActivity.this, "+8801844097722");
3. Placing a paid call (audio only):
ReveSaaS.makePaidCall(activity, numberToCallWithCountryCode);
Example
ReveSaaS.makePaidCall(MainActivity.this, "+8801844097722");