Hey guy! Apple announced the antenna issue in iPhone 4, did you have problems when holding tight the iPhone 4, how we should holding the phone or what can we do to improve the signal?
I think you can do nothing about it (except for holding the phone with two fingers -> looks ridiculous). Because of the wars of Apple and Nokia, Apple couldn't use Nokia's antennas anymore, and this is how it affects. I'm afraid that I'll change to HTC, they're offering much better phones nowadays.. :/
You could return your phone; they finally did the honorable thing and stopped charging the restocking fee for these broken phones. Then spend your money on a DroidX (best network overall, best phone on that network), Incredible (best network overall), or Sprint EVO (3G and cell are not as good as verizon, but the price is less, and they offer "4G" (really 3.9G, but it is still faster than 3G).