My iphone 4 never gets service?

My iPhone 4 never gets any service anywhere, sometimes it might pick up 2-3 bars outside but then it goes away instantly, i never get it in my house and my area has good coverage, i've tried new microsim, resetting the phone, hard resets, airplane mode on/off, nothing works, i think it might be the aerial that is faulty but i don't know, help would be much appreciated.

Speak to your service provider about possible issues with the phone.