Mtn can't be trusted

I did an upgrade on the 27th January. With no pay in costs. I even asked the agent doing my contract and she said no pay in fees. I read my contract and it has no mention of extra fees to be paid in. My installment is R769 but they hit me with a bill of R2351 I contacted them....135 call center....they sent me to the store where I took out the contract. Apparently they can't change it on the system. I had to pay the R2351 Imagine.....how deceiving is this service provider. I don't trust them anymore. I won't do another upgrade after they have ****** me like this. Personally people should be careful when dealing with mtn. They are clueless and their call center agents can't help. They either cut the call or pass on the buck.