Why can I hear music loud and clear on my mobile phone but I can't hear people talking through the speakers?

I have a samsung D500 mobile phone. I can play mp3 music off my phone without any problems but when it comes to people calling me, I can't hear them but they can hear me. What's wrong? I don't want to spend $$$ on another phoneWhy can I hear music loud and clear on my mobile phone but I can't hear people talking through the speakers?
take your phone to the phone retailer whom you brought it fromWhy can I hear music loud and clear on my mobile phone but I can't hear people talking through the speakers?
It's because the terrorists have won, Johnny.