Help problem with htc incredible s when talking on phone!?

[bellajessica]

I noticed this problem today, when someone rings me or i ring them i can barely hear them unless its on speaker phone. when its not on speaker phone their voice is all muffled and low and i cant hear them at all. the in volume for calls is up loud. can anyone help me with this issue? ive turned the phone off and on still isn't working and normal sounds like for games etc all work fine please help