Help Cannot hear calling party


Hey guys, i just bought a samsung galaxy ace GTs5830c android version 2.3.6 , all works perfectly but i have an issue when i receive a call or when i make one, i cannot hear the other person but they can hear me perfectly, i wonder if this is due to hardware issue or a configuration thing. I reset the phone to factory default with no additional software installed and have the same problem, with speakers works perfectly. Hope have some feedback regarding this.