Hi. I have an Acer Hi. I have an Acer Aspire 5720z. I am having a problem with my voice call

Question

Hi. I have an Acer Aspire 5720z. I am having a problem with my voice call using the yahoo messenger. I have test the mic and it seems to be working. The problem is, I can't hear the playback. When I would try to call someone, I couldn't even hear the ring, and also when someone is trying to call me. I have gone to the audio device and made sure that nothing is muted or whatever. I've really run out of solutions. Thank you for your time.