Telkom is a ****

Telkom keep debiting my account even though I've canceled my month to month contract with them. I unemployed and every time they try to debit my account there's bank charges. I'm struggling to pay any of my debt because Telkom tries to debit my account atleast 3 different times in a month which mean when I actually do have the money to pay, my account is so far in a minus, it's impossible to pay. I don't know what else to do! I canceled the contract on 6 May, called the useless customer service agaib on 20 May to make sure that the service has been canceled AND THEY CONFIRMED! My account is atleast R450 in a minus due to telkom debits every month and I don't know what to do.