@tigerpro Thanks for the info.Dang, I'm stuck with two of these 910F's that I bought (new in unopened boxes, even though they are 6 years old).

Just installed Ubuntu Touch via UBports on a Samsung Galaxy Note 4. Got a pre-paid SIM card from AT&T. Everything works, sends & receives text, plays music, keypad sounds, even rings when someone calls, can dial out and the other phone rings, however there is no audio at all on the phone call. The other party can't hear me and I can't hear them. Don't ever hear the phone ringing when dialing out. I've tried the speakerphone, headphones & bluetooth, no sound on phones calls. Can't figure out if this is a Ubuntu problem, Galaxy Note 4 problem or a SIM card AT&T problem. Anybody got any ideas?