I have an HTC ONE M9 using Android 6.0, Sense 7. It was a T-Mobile Phone that got locked out of their network for nonpayment. I use H20 SIM (On AT&T network) and I cannot send MMS. I've reset the network settings, APN, and the phone. I've used different messaging apps-all with negative success. Any advice you can give would be appreciated. Now apps like KIK and Facebook work between those programs but not for sending MMS to phone contacts. SMS is unaffected.