VERY BAD SERVICE RECEIVE FROM MTN!!!

I am very unsatisfied with mtn since the 03/04/2015 I have been struggling to get my upgrade which was due on the 01/04/2015 I wanted the SONY Z3 I received the phone but the next day my contract was terminated due to the credit limit so I took the phone back and cancelled it. The same day of the cancellation... I went to mtn in Clearwater mall, the consultant that assisted me there said I should come back on Tuesday he is going to sort it out, Tuesday went he said he needs all my info then he will call the credit controller, I went all the way to clear water mall to give the consultant my info when he could have taken it the Sunday when I was there, Wednesday came he called the credit controller to increase the credit limit he said the credit controller says he is unable to increase the credit limit with no valid reason. I am very frustrated at this point. I keep phoning 808 to speak to a consultant but it keeps ringing, im starting to think nobody works at MTN.This has cost me numerous emails, <br> phone calls , fuel and that just because a simple contract could not be upgraded. <br>