Setting up voice channel
A SIP trunk is needed to carry voice calls between the telephone network (PSTN) and Sinch Contact Pro. You can enable voice calls by:
- 
        Subscribing to SIP trunk and telephone numbers through Sinch Voice API 
- 
        Subscribing to SIP trunk and telephone numbers from any telephone operator 
- 
        Providing SIP trunk and telephone numbers from your own or managed IP PBX or SBC 
