Hello people of the Fediverse. I have a minor problem I'd like to pick your brains for any solution, regarding #xmpp / #jabber calls over AT&T wireless mobile, in the US.

Simply, xmpp calls over #att data fail, audio or video doesn't matter, texts get through just fine. Calls over WiFi are fine. I have tried the aTalk and the c0nnect pro apps, same result. Using chatterboxtown.us as a server, in case that matters. All devices are Android.

Looking for clues, knowledge or experience. TIA