I have an iPhone 6s plus with t-mobile. It works fine most of the time, but sometimes, it has happened a few times, where I would get phone calls, and I would not even hear the phone ring or vibrate, even though I have vibrate on, and the ringer on loud setting. I miss class like this with frustrated callers saying it goes straight to voice mail. I would also notice that sometimes callers that I have in my contact list would show up in my missed recent calls as unknowns, like they are not recognized, and other times their name shows up. Other times it is fine, and my phone rings and I pick it up. I do wear my phone in a belt pouch thing, with my phone up against the inside, since I do not like carrying a purse. Could the class be getting cut off with pressure on the front of the phone in my pouch? I am running iOS 10.2 on the phone. With raise to wake feature enabled.