Failure to close my account and keeps on charging me!

I paid off the account and sent an email to the collections department to instruct them to close the account with immediate effect. Was informed to contact Edgars directly and was given an email address. Sent the same email to that address, no reply, sent a follow up, no reply. Received a message from MDP attorneys this morning to say I need to pay the promised amount. NO!! It was paid in full. Why must I cough up another R500 due to this failing company's non existent admin systems? This is unacceptable. Who do we contact?