HELP iPhone 5s randomly losing service but not really?

So this has happened a few times to me now, and its completely random. For whatever reason my phone will lose all data service, in locations that I know for a fact that i have it, like my bed room. The problem is that it doesn't say anything to me about it. It still displays 3 bars of service and LTE logos. I know I'm not in a bad zone or anything because it's literally random. Happened to me when i was on campus the other day. It happens when I'm not using my phone too, and this is the real problem. When this happens, I don't receive any notifications because the phone can't receive any. To make matters worse, this means i cant get imessage alerts from people sending me texts. Originally when this started happening i restarted my phone, but now I've realized all I have to do is turn on wifi and turn wifi back off and the problem is solved. Please help this is incredibly frustrating. Oh and my service is T-mobile