MTN Incompetency and attempt to ******* the subscriber.

I get a notice that I can now upgrade my cellphone account. I am now told that MTN have adopted Vodacom's renewal and that I need to pay to get out of the contract. I explain that I am simply upgrading, and they say that I have to pay the outstanding device payments. Fair enough except that the device payment is R 713.04 X 4 = R 2,852.16. No, according to the call center operator, it is R 5,875.99 (which is the outstanding contract X 4 and not simply the device). I point this out and I am told to speak to customer service who confirm the theory and can see the problem but cannot help and push me back to the upgrade lady who then says that she can't help, I cannot believe the level of incompetency and knowledge that I am experiencing on this call center engagement.