Telkom ******* blacklist

Good day, I had a sim contract with Telkom but it was always out of service/no network. I went in store to enquire about this and I was told to be patient they’ll work on my matter. Few days later still there was no connection I then decided to cancel my contract with Telkom and I was told because it’s a sim contract there won’t be any hassles with cancellation. End of the month they debited my account even though I had not used data for that month. I reversed the payment. Fast forward to today I receive a call from the lawyers that Telkom has blacklisted me and I now owe them R1600!!! But how when I only reversed R199 and rightfully so?!