I am guessing it is software. Mine also worked well for the first day I had the phone then it stopped. Also the tech support guy told me some iOS users had this problem when iOS 9 first came out and a software update fixed it.
Just got off with AT&T and they disabled HD voice and everything seems to be working for now. He said there seems to be an issue with the current software and HD voice
I can send MMS fine but am receiving them only sporadically. I have tried rebooting, removing the sim card, and manually entering the APN settings. Any other suggestions?
I have turned wifi off and on and mobile data is turned on. It was working yesterday now it is not working at all. Did manual APN setting and am receiving some group MMS but cannot send photos in group or individual SMS