Cell C
Continued Debit order despite contract cancelled

My cellphone contract expired in December 2012, and since my daughter was no longer using the line, i popped in at Gloden Acre branch to cancel the contract. I was advised that no more debit orders would be processed. When i checked my banking account at the end of February I was amazed to see that Cell C had indeed continued debiting my account with R50 even though the contract had been cancelled. I then put an online stop order in place. Since then there have been three attempts to deduct from my account, resulting in bank charges being levied against me. Please can Cell C stop this action immediately and send me confirmation that this has been done? Also there is the issue of refunding those debits.
This is most annoying.
SW