Only works on speakerphone?!

Yesterday, I went to make a phone call and although the call connected, I couldn't hear anything. The person on the other end later told me that they could hear me perfectly.  I tried turning my phone off for a bit, then calling again, but it still didn't work. Then I turned it off for a few hours and let it charged (the battery was only half-full), but no luck. I decided to try calling someone then switching on speakerphone and only then can I hear the phone call. I decided to try this because the same thing happened with my Samsung A737.
I've only had my Impression since January, and the water indicator is absolutely fine - still white.

So, has anyone else had this problem or have a possible solution? My contract doesn't end for a little over a year, so it would be quite expensive for me to buy another phone without any 2-year contract discount

I haven't dropped it recently, and it hasn't gotten wet at all.

i had the same problem. eventually your screen will start changing colors and acting weird. its the flex cable that needs replaced. where it bends back and forth and rubs between the two halves of the phone it wears out the edge of it and exposes some of the bare wire. you can get a new flex cable with tools to fix it on ebay for 8 bucks shipped. if you need help with how to take it apart and replace cable send me a pm and i will do my best to help you out.

Oh, cool. Nice tip. I don't think it's the motor, because not only did this test work, but it always vibrates when I get a call. It vibrates again when I get a text, but every once in a while it will stop for a day or so.