Poor Service

I approached Hellopeter on the 3 April 2016 about my Sony experia Z3. I received a response from Hellopeter and MTN on the 10 April 2016 and no progress has been made since then. I've been to MTN stores several occasions and no consultant is able to help nor the managers, how pathetic can you be? As long as my payment is deducted each month then all is well, lets just say I don't pay then MTN would breath down my neck but if they don't deliver on their service, then what? I'm not taking the Sony Experia Z3, I want a Sony Experia Z5 at no extra cost, giving me a Z5 would be way easier to solve than this circus that is currently taking place. Mtn is acting like a bunch of amateurs!!! I cannot express my anger in words!!! Its PATHETIC!!!! Siphumezo Ndokweni ( High Value Pre Paid Call Centre Agent) was the one who assured me that the situation would be resolved. I e-mailed Siphumezo on the 15 April 2016, received a response on the 20 April 2016 and the trend continues. When will this situation be resolved? Or should I just change networks to make things easier???!!! THIS IS THE LAST TIME I'M COMPLAINING ABOUT THIS!!! I'M SERIOUS!!! THIS WILL BE RESOLVED WITHIN THIS WEEK!!!