******* contract upgrade

I have recently noticed that i was being debited extra from vodacom. When i called them they said i have 2 contracts with them (which i do) however they informed me that my data contract was upgrade at alberton city on the 13 december 2014. I did not upgrade that data contract which should still be R99pm but is now 779pm. I logged a call with them and refunded 1300 for 3 months and was told that the contract will be cancelled. This is not the case as i am still being debit the extra 779pm. I need this sorted out asap.