CANCEL CONTRACT ASAP

On the 02 May 2015 I upgraded to the Sony Xperia Z3. On the 03/06/2015 the phones screen goes black on me, and I took it back to the agency in Randburg Square. I haven't seen the phone since. I called in to the call centre to query why it's taking so long, I mean the warranty should cover it. I was told the phone is still in Randburg. It's going for 3 weeks and I still don't have the cell phone. I am told that I can take the phone to the repair centre in Midrand. I mean is that how MTN treats their customer's. The phone I upgraded to was R499.00 a month. I get a statement now with an amount of R725.00 that will be deducted. what on earth is going on here. Go through my profile, please tell me when I gave you guys a problem, when was a debit order ever returned. I will not tolerate this kind of treatment from MTN. I've been too loyal and clearly I am not VIP enough to get the treatment I deserve. PLEASE CANCEL THE CONTRACT IMMEDIATELY. I WANT A REFUND FOR THIS NEW CONTRACT, OR I WILL REVERSE THE DEBIT ORDER AND YOU WILL SEND ME A BILL FROM THE PREVIOUS CONTRACT I HAD. THE CONTRACT SHOULD END 05/07/2015. I want nothing to do with MTN.