Terrible service in upgrading contract

I have been a loyal MTN client since 199 and am very disappointed in the service I received in upgrading my contract. I had a Shockingly bad experience in trying to upgrade my MTM Contract. I agreed to an upgrade telephonically, when the DebiCheck came through the amount was more than 3 time what I agreed so I did not accept it. I tried calling MTN to discuss changing the amount on the Debi Check and was put through to 5 different agents without any resolution. I tried explaining that I am not comfortable accepting an amount different to what I agreed.