Iphone 4s strange loudspeaker issue.
 

The loudspeaker on the bottom of the phone doesn't works during calls. The earspeaker works fine and the mic too. I can make calls perfectly fine, but not place the call on the loudspeaker. However, loudspeaker works fine when i play music/videos or sounds. It rings loudly when i receive a call.
It just doesn't work when i want to put a call on loudspeaker.
What might be the problem?

Try to change the charging pin.

I just cleaned the connector and it worked. Thanks!