Is it possible to change the audio integer(the one on the motherboard)

Apparently I sold my iPhone 4 because it had a broken home button and speakers. He got the home button working but says the speakers won't work even after changing the charging port(I thought It was the problem and I had told him before) and says he found a dude who can fix a "crack" on the motherboard, who will change the audio integer. He wants me to pay half of it but I need to know if it is possible or not.. Otherwise he wants me to buy back the iphone.

I really don't think this is possible