It's the end for me with mtn

I have been a client for over 12 years but now I can say they are the worst company. They want 2 charge me over 5000 for wanting to cancel my upgrade which I had for 2 days. They sold me an idea for 2 phones but I ended up getting only 1 hence I wanted to take it back as they couldn't deliver on what I wanted. The consult at East rand mall tried to deliver but in the end he didn't and never had the decency to call me back. He actually left me in a limbo.