since last night, while in the middle of a call, i heard a crackling sound from the receiver after which i can't hear anything from the receiver of the iPhone. all the other sounds were perfectly fine and its not "tricked" into thinking the headphones are in. i can hear fine on speaker and while the buds are in. even more strange is when its on speaker and i cover the speaker at the bottom next to the dock connector, i can hear some sound from the receiver :S

i have tried the various tricks that i have read around the internet such as:
plugging in earbuds while listening to music or on a call, repeatedly
resetting the settings
reset iPhone
restore iPhone

the iphone is unlocked and not activated, will the apple store help me or will they reject the iphone and refuse to give me support?

any help would be greatly appreciated