Round the buouy again

Upgraded our mtn contract on 07/05/14. New model phone Sony Experia Z1. IMEI number *** Within a week first problem, Phone works fine but cover seems to be open? For a waterproof phone? Sent it away. Come back reported as physical damage. Brand new phone! Please Pay R1200. Asked for phone back. Phone now struggles to hear when someone phones. After two three months the phone had to have charger in to switch on. after another week did not want to switch on at all. Sent it away again this time, Please pay R500 to fix. We declined and asked for the phone to be returned. MTN asked again if they must fix it at cost? We refused and asked for the phone back. We dont want to pay for fixing a phone that we hardly had the opportunity to use. Still no phone, now in may/june 2015 we receive sms to pay for service charge. We have been paying this contract for a year without a phone. We want a new handset or this contract to be stopped! In order to have a phone we went to a competitor to get a new contract! Ill pay the service charge if mtn reimburse me for the time that i did not have a phone.