Cancelled the 2 contracts,my account still debited

My 2 accounts have gone past 24 contract. I never received any call/ correspondence from Cell C on whether I still want to continue with the contract. Beginning of July I cancelled my 2 accounts after a large amount was deducted from my account and I was told that has been done. This morning I got a shock of my life R9915.00 has been deducted from my bank account. This is totally unacceptable. How am I going to pay for my son's school fees and other things. I want this transaction reversed asap and I need to know why was the money taken from my account because I cancelled those sim cards. I also want to know why all of a sudden large amounts of money are taken from my account I never had any problem during the 24 months contract.