Billed incorrectly

So Telkom has decided to charge me a penalty because I closed my bank account 14days before they could deduct. This is after I called them and informed them of this and that I had to close my bank account urgently due to unauthorized transactions. Consultant told me at the time that this was no issue as long as I pay it. Now I have been penalised as if I didn't pay my Telkom account. This is wrong shame because I shouldn't have to explain to Telkom why I am closing my bank account, I thought I signed a contract to pay everything. None of the other companies had an issue with this, just Telkom.