Yesterday I received my iPhone 4 from UK,today I had time to test it out and I realized that top speaker is not working. Bottom speaker works just fine. I've taken off the protective film from the screen and the back,and made sure it's not on mute. I'm running ios 4.01 if it matters. Just to be precise,when I receive a call,I can't hear the other person unless I turn on the bottom speaker. Does anyone have an idea?