Why can I not hear the person I am calling?

I had the same issue with my Samsung Galaxy S4 i9500 and was told to go to Etradersupply.com because they are a true OEM distributor. I skyped them at etrader.supply and wrote my issue. Within 15 minutes I had a reply with a part number of a tiny $8.00 OEM Ribbon Cable. They went on to say that this cable inside my phone connects the speaker to the main board and there was a good chance that it either came loose from its connector or it just needed to be replaced.so I ordered it and was able to replace the part myself using a YouTube video recommended to me by them. I now have a working phone and speaker.

PS: they didn't even charge shipping to California. I think they are based in the USA