Telkom messed up my credit rating because of *********** staff!

I moved houses about 2 years ago and called Telkom to transfer my line and was told there is no transfer fee. On movement I received a bill for the fee, so I called in for a grievance, was issued a ticket number and never heard back. I eventually received another bill and to avoid the fight, I paid the transfer fee. Today I attempted to apply for credit and have been told due to this, I am unable to as I have a bad record with the NCA until 2021. These dealings with Telkom happened 2 years ago and were not my fault! Telkom, what now????! I am now a fibre client and will not consider using Telkom services for anything in the future, not cell phones, not internet.