Are my phone calls being intercepted?

For some reason when i'm on the phone I hear REALLY odd static noises and sometimes it sounds like something is interfering with my phone call because I can sometimes hear people talking but only for a split second. I currently have an iPhone 5 and i'm with T-Mobile. Its not my phone because I just bought it about a week ago and its been happening with the few phones that I had before this one. I noticed it mostly happens at night but I have no idea what it could be.

maybe it is an cominucation error

When a telephone is tapped or intercepted by authorities with a court order, you hear nothing from the equipment that does it. I would suspect you have a radio transmitter of some kind nearby, possibly mobile units that are passing and their power level is just overriding your phone. Pay attention to where it does it. If it only does it in one location, that's most likely the cause. If it does it everywhere, you should take the phone back to the place you bought it. In thart case, you may have a defective phone.