MTN CHEATS ME OUT OF CONTRACT

I took my brand new sony xperia m2 back to Ucell/mtn store at Durban,game city branch on 29 September 2015.The phone was over heating and switching off on its own.I was told by the consultant by the name of Bilal that I can not get a new phone because I was 5 days late after 6 months warranty.He informed me that Ucell/mtn would repair the phone as it is still under contract.After giving me the run around for more than a month Bilal hands me a phone that is switching on but unable to perform all the functions it could prior to repair of the battery.When asked if he could assist me further by sorting this problem out his response is there is nothing he can do to assist me.Im currently paying for a phone that I cannot use.?I went to MTN on the bluff and the staff there are very helpful.They took the time to try and sort the problem out.They informed me that technician would have to look at the phone. A technician at mtn pavillion branch checked the phone and says the phone needs to be booked in once again.Im afraid that mtn is stalling to prevent repairing the mistake they have made or giving me the new phone that I \I was 5 days late""""