Wont Repair My Phone

I have a Sony Xperia V on a contract. about 2 weeks before my contract was a year old the touch part cracked due to the battery overheating, i took it to mtn and they told me i have to pay over R2000 to have it fixed because its physical damage. but how can it be physical if it cracked under the glass and you couldnt even feel it. i asked the manager and he started screaming at me and my husband. they also sent it to the repair center so i could get the price of the repairs and when i got it back still broken in had extra damage to it including scratches, missing cover and a chip out of the conet of the phone. i showed the manage and he told me its not his problem. i must just pay the price. so now im here 7 months later with a broken phone that they still wont repair for free even tho they damaged it worse than when i took it to them. NOT HAPPY MTN!!