How to receive incoming phone calls?

### This issue is for a:
```
- [ ] bug report -> please search issues before submitting
- [ ] feature request
- [X] documentation issue or request
- [ ] regression (a behavior that used to work and stopped in a new release)
```

### Description

We are using PSTN phone integration, and were able to perform outbound calls from the Web Sample towards the phone number.

But we were not able to receive incoming calls, as we found no way to indicate the phone number of the client.

Is there a way to do it? (The UI suggests that there is a way of doing it.)

Thanks,
Yehoshua