iphone 5 signal loss

I've had my iphone 5 for a while now and I'm always experiencing this problem with my iphone. I'm not sure if this is just my carrier or if its the phone itself but every 4 or so minutes the signal bars on my phone drops and then shows the "No Service" sign. And then sevral seconds later my signal goes back to normal. Again I'm not sure if this is just my carrier or if its the phone itself. I don't really have the time and effort to go to the apple store and ask. I've had replace my phone before but not for this kind of case. I don't think they're gonna give me another free replacement.