Disgusted with phone repair

I took my Sony M4 phone in to Vodacom Brooklyn because the microphone was not working. People could not hear me when I was talking to them on the phone. The phone is about six months old and I have it on contract with Vodacom. The Brooklyn branch send it in for repairs and when I got it back the phone still had the same problem. I took it back to Vadacom Brooklyn and they advised me to take it to the Vodacom repair shop in Menlyn. I took the phone to the Vodacom repair shop in Menlyn and they send it in for repairs. They phoned me about a week or two later and said the quote to repair the phone was around R2500. I complained that the phone was under guarentee. They said they would get back to me. I got an sms after about a week and a half stating that the phone is back at the Vadacom shop. I went to fetch it and the phone was not working at all. I discovered that the back panel was loose and the phone did not even charge or switch on. When I inquired about all this the repair centre of Vodacom said they are not going to repair the phone because it had physical damage. I gave it back to the Vadacom shop in Menlyn and am trying now to find out what physical damage it had