iPhone 4 signal range not strong enough?!

As I understand the iPhone 4 has a lower sensitivity radio as well as what has been termed an engineering flaw in regards to antenna design.

If you use AT&T as a carrier you should know that AT&T's network use GSM technology, an inter-national standard. This means that your phone will work overseas, provided you outfit your service plan accordingly. However this also means that your device uses higher frequency radio waves to communicate than the US only carriers such as Verizon or Sprint.

Simply put, the higher frequency radio waves allow the information to travel farther, and faster, but is attenuated, or dampened down, by solid objects such as buildings.

In conclusion, I believe that an unfortunate convergence of factors have led to your loss of service in certain areas. The iPhone4's noted poor reception and the GSM signals inability to penetrate buildings, have culminated in your loss of service.