Forced debit orders

I was retrenched in December and I have contacted cell c multiple times to remove the debit order from my account. They have refused, even though I have never missed a payment. They have debited my account again and the payment failed just like I said it would. Now I'm being charged by FNB for the failed debit order attempt. To add to the stress I receive a statement from cell c charging me a penalty for the failed payment. Mind you the account is still not in arrears because I'm paying them directly! I even asked someone at one of the stores and her solution was that I must pay the account 5 days prior the debit order date. Who's this solution for? Me or Cell C???? Can't wait for my contract to end in July, I never want to deal with cell c ever again.