Hi: Just bought an Iphone this weekend & it is virtually unusable for phone calls unless I plug in the ear phones. I can hardly hear the person I'm speaking with at the max volume with or without using the speaker phone. Is there some setting I can change or do I need to take the phone back? I bought this at a local ATT store. We don't have an Apple store in town. Would I have to return it to Apple directly or will the ATT store look at it or take it back? Thanks much for any info!