Cell C Contract phone

Hi..I would like to share a very bad experience with Cell C contract phone.They deducted twice on my account without my approval.December they had to deduct but it bounced back because of no funds in the account,I called to check with them how much was left for me to finish off the contract because I knew it was ending 8 January so the lady I spoke to told me it was R474 that was going to be deducted hense it was R70 extra on the 474 because they didn't receive funds so it's an interest fee which I didn't mind.Yesterday the deducted R404 and R474. So now when I call them Iam told the contact was canceled without my knowledge how do they do that because what if I wanted to continue with them now I am told the other extra amount they took was because I didn't pay December yet Iam told they canceled the contract and they even blocked the Sim card I did not receive data n minutes so why iam paying extra R404