billing and incorrect upgrade information

My Mnt current contract is about to expired next month of feb i got a call from a guy by the name of <br> Thulani Welcome Manzi from MTN informing me about an upgrade to my contract since my current is ending<br> ..i have 3 lines that are on contract and all are due for an upgrade but i told him that i want to upgrade only 1 line and put the other 2 numbers back to pre-paid when we disscussed the upgrade i asked him serveral time if i upgrade what will happen to the amount i am currectly paying (R257) he said nothing will change until 30 days later after i receive my new upgraded device which i will pay (R228) for it, the upgrade took place on the 16th for january 2016 but on the 20th of january which is the debit order for my current contract to my surprise they debited me R472.00 but initially i was told on a recorded line that nothing will change until my upgrade...so i just want my contract to end and cut tires with MTN because we started a new year with problems, i have received a new device its still not opnend i want to return it<br> .on the 21st of jan i called their 808 number spoked to a guy by the name of Ernest Mngema said he will escalate the matter which will take 24/48 hour