My iphone 5's ringtone won't go off, how do I fix it?

When I get a call, nothing happens. My dad says it goes straight to voicemail, but I don't even see my phone light up and it doesn't say 'missed call' either. It only rings when he tries a lot of times. Same thing with text messages.
I just want some help to see if I can get it fixed before I go to at&t

here is what I tried:
-making sure it isn't switched to vibrate
-closing all other apps
-turning it off and on again (did this a lot of times)
-going into sound setting and making sure it's on
-and last, taking out my sim card and putting it back in

Sounds like it has an active divert.
Go as I'd to set up a divert and remove it