Blacklisted me, yet they owe ME money

I cancelled my contract with Telkom On the 4th of December 2017. For months afterwards Telkom billed me. Everytime I had the debit order returned. Telkom then kindly blacklisted me. Turns out, they OWE ME R850. I’ve sent mails, made phone calls, visited branches. Think my problem’s been sorted out? Oh no. Telkom, please know that the amount you owe me is FAR less than the loss I have been causing for you by telling everyone how pathetic you are.