Can you tell me a web-service of ip-telephony with a good API?

Question

API

1. Web API requirement:
- input ("on the fly") of arbitrary user phone numbers,
- call with playback of a pre-recorded message (sound file),
- event detection function - the user accepted the incoming call, while the response delay is <150 milliseconds .
2. Must support calls within Russia, including to mobile phones.
3. It would be nice (but not necessary) for the service to use some kind of Moscow telephone gateway so that users receive calls from a Moscow landline number.

Answer 1

Look at this.

Answer 2

I can recommend westcall westcall.spb.ru/corporate/ip_services/sip/
If it is required for large purposes, then it will definitely fit. We have 200 employees on it.

Answer 3

You can try VoxImplant , it satisfies all requirements