I'm having trouble with my FaceTime?

I've had my iPhone 5 for 2 years now I bought it brand new. For the past 2 years when I FaceTime audio my boyfriend it will work then cut out so I can't hear him but he can hear me still and no it's not my house internet because when he comes round and talks to his mates on FaceTime audio it works perfectly fine doesn't cut out. I just wondered if it was my phone or if anyone knew what else it could be?

Take it too the apple store

Poor visibility no pictures