Poor Service

I have been an MTN client for over 10 years now may be longer. I was at the MTN store in Cresta on Saturday 25th July 2020. Luvo Booi was the consultant that assisted with me with an early upgrade. He advised me that there was an amount of R804 that could be added to my bill for August 2020. My early upgrade was then approved by your Vetting dept and after going through the entire process after being in the store for more than an hour an amount of R5292 came up as the amount due upfront. The consultant nor the Supervisor could not answer me as to why there was that amount. I then called the Call Centre and was advised to call the Retensions dept today. After explaining the issue the consultant demanded that I pay R907.09 upfront which I refuse to do. I was told that it can be added to my bill which I am sticking to. I was advised that a Supervisor from the Retensions department will call me within 24 hours which I feel is so wrong as I am a loyal client and I am being treated like I am a client from yesterday. If my request for the fee to be added to my next bill cannot be approved and my early upgrade granted to me then I will rather cancel my contract and move to a Service Provider that knows what Customer Service is all about.