Can you actually USE an iPhone in either AT&T or Apple stores? I currently have a S/E T637 and it often drops the voice of the person that I'm talking to. It makes me ask the other person have to repeat stuff often. And this is when I have "full bars" of signal strength. I wonder if it's that I'm in poor coverage areas or is it my phone. What I'd like to do in-store is to pop my AT&T sim in the iPhone and make a call to compare A to B the quality of the two phones.