Bill statement over charged

I have received a statement with an over charged amount of R341, 25 and also the refund of R884 was reversed which I do not understand. I called Vodacom and was told that the amount charged was a pre-mature cancellation fee of a contract and a dispute was lodged with a reference no. ***, however I am receiving messages that I have to settle that amount. My contract was never cancelled pre-maturely because the contract was never authorised by me in the first place, so vodacom should not charge me that fee and I request that vodacom to reverse all those charges as I expected my balance to be less than R800 because of the cancellation of disputed contarct.