is twilio (the voip provider) supported? i didnt see it in the lists. do i just enter the data manually?
Yes, you will just enter your Twilio SIP username as{user}@{domain}.sip.{region}.twilio.com
{user}@{domain}.sip.{region}.twilio.com
For example:
alice@contoso.sip.us1.twilio.com
And the corresponding password for that user, which you have specified in the access control lists.
See the guide here: https://www.twilio.com/docs/voice/api/sending-sip
If you haven't set up your SIP Domain, start here: https://www.twilio.com/docs/voice/api/sip-interface