Contract cancelled but still paying!

I cancelled my 3G contract with Vodacom early November 2015, paid my early termination fee and requested confirmation that the contract had been cancelled. After no response, I put up a complaint on HelloPeter and was eventually contacted and confirmed the contract had been cancelled. Low and behold, at the end of December I get statements showing I had a credit with them - I should never have received statements on a contract that was confirmed to be cancelled! I contacted the lady who assisted me previously and again she confirmed the contract was cancelled and I should not worry as no money would be deducted on the 1st January 2016 as that was my main concern after receiving statements. What bull-****! An amount has been deducted that is much more than the original contract was for! I have sent this lady an angry email demanding a refund and asking why they are still taking my money from me if the contract is CANCELLED! Such pathetic service, I never want anything to do with Vodacom ever again and will always talk anyone out of using their services.