MTN Retentions Department an absolute failure and disgrace

In January 2019 I decided to finally upgrade my phone contract with MTN. I was informed that my current package MTN Choice 1000m was discontinued and should I decide to upgrade I would have to choose another package Following a review of all available packages I found that there were no similar priced packages for the same value minutes and data. Vodacom packages offered better value so I decided to cancel my contract with MTN. When following the cancellation process I was referred to the MTN Retentions department who eventually offered me a deal match package. I decided to stay with MTN and settled on an Iphone XS for R1649 VAT incl per month.

Everything went well until the phone arrived.... wrong colour..... So I went through the process of returning the phone and finally after a few weeks wait got the right colour phone. Then the billing changed over to the new package and this is where the painful journey really started.

The first adjusted bill was incorrectly charged at R1911 instead of the agreed R1649. After receiving the second incorrectly charged bill for the same amount, R1911, I made contact with the same MTN Retentions employee who initially helped me. Several emails later and a couple more incorrect bills I was told to contact Customer Service, only to be told that only Retentions can sort out the problem. So back I went to Retentions, 4 x inquiries later (last query reference is (# 1- ********** 187) and I was informed that it was a historic recurring data bundle subscription fee which was incorrectly carried forward and charged to my upgraded account since January 2019. At my last inquiry I was promised that the subscription was going to be cancelled and a refund retrospectively credited against my account. The discrepancies in my bill are still there, no sign of any credit, plus recently I've been charged more than what the latest bill was issued for.

I'm sick and tired of spending hours on the phone, at work, only to be issued with a new reference number which does not resolve anything at all. Never have they offered to phone me back to follow up on the matter. I would appreciate if the issue could be escalated and that someone senior at MTN can look into my case.