Cell Phone Repair

I took an Iphone in for a screen & microphone repair. Collect the phone 6 hours later and screen replaced, but microphone not working, neither the screen sensor. Get told "no problem, will sort"...Phone them the next day...yes, phone is ready. Get there, and there is no change from the previous day, although I get told the phone is working, but not the microphone...its a "software problem"...download and update-no change. They then offer to write a letter which I can teke to Apple or Cell C and get another phone !(seriously!!). Threatened to contact FNB to reverse the credit card payment before they refunded