AT&T iPhone 5C Service Issue?

So I have an iPhone 5C carried by AT&T and Monday I ran into an issue. My service just dropped abruptly and suddenly out of nowhere. And it's now Friday night and the service just comes and goes. I can sometimes by myself a little bit of service time usually 10-20 minutes max. And then it just drops. And the weird thing is when the service drops, FaceTime doesn't work even with Wi-Fi which confuses me. Someone please give me an answer to this please

Call att to see if the problem is on its end.