MTN Misleading Upgrade offer

I'm really disappointed in MTNs Customer service and their misleading advice when they did an upgrade on my contract. 2 months before my contract was due to be completed, I was contacted by an MTN Telesales agent who offered to upgrade my contract to a new contract. I decided to go to the MTN store in Mutual Park Pinelands where the sales agent offered me an upgraded deal which was much cheaper than my current package. When agreeing to the new contract I was advised that my 1st bill would be high due to Pro-rata charges for upgrading, however, my 2nd invoice was still higher than what we agreed when upgrading. When I contacted the sales agent that did my upgrade she advised that I'm being charged for my old device and the MTN new billing system is unable to change the charges app**** for my old device. What is the point of MTN upgrade sales team contacting clients to do an upgrade and then still charging them for old device, this is very misleading. If this was explained to me initially I would have not upgraded in the first place. Please give me a call to sort out this issue. Thank you