Not cancelling my account a year ago

My cellphone was ****** last year and therefore decided to cancel my contract. I asked for the exact amount to owed to Cell C aswell as the account to be cancelled. To my surprise a month ago I recieved an SMS saying i was credited airtime which was part of my \cancelled"account. I then went into the branch in Golden Acre to phone cancellations and cancel the contract myself. I have now recieved an SMS saying I owe R97 on the cancelled account. I dont believe I am responsible for this amount as I did ask for the exact amount and for it to be camcelled a year ago. I now owe bank charges of R120 as I did not have the availible funds. I am fed up with Cell C and their lazy service. I refuse to pay that amount"""