Telkom hidden costs on sim-only deal

Had a 24 month LTE contract with Telkom that came to an end on 03 December 2020. Called 180 to cancel the contract after 24 months as I was going with MTN for their better service. They then offered me a wireless broadband month-to-month deal instead that was more affordable and I stupidly took it. However, when it came to 1 Dec 2020, they upgraded me but then added an extra R60 (that the service advisor never told me about) for using my own router and I only took the sim-only deal. What a mission it turned out to be just to cancel it as they want me to pay the extra charge with 30 days notice ref *** given. This lady then said if I don't pay the full amount, it will reflect on my credit score. I even made a recording of the woman giving me the contract as proof, but they don't seem to care. With MTN, I will rather pay the extra amount but I am done with Telkom. They quick to sign you up to a contract but want you to wait months to cancel you when they misinformed their own product.