Wow! Ive had this issue for 3 weeks since replacing my lcd and screen, all i did was removed the "do not remove" stick and screw, pushed the little copper piece up a bit. Turned the phone back on and boom full signal and working fine!
I have the same issue since i replaced my iphone 3g 8gb lcd and screen my phone fails to get signal except on 3g occassionally, it sometimes comes up with normal signal if left for a while but still doesnt make calls, and/or the call fails all the time. also wen i do get to make calls on the 3g people fail to hear me after about a minute or so......help! ive tryed everything! thanks