BLACKLISTED DUE TO THEIR MISTAKE!!!!!

I've been a client with TELKOM forever. I had a landline for over 20 years and I've paid my bill every month. My time with TELKOM started roundabout 1996, and I've never missed a payment, my bill was settled in full every month. In 2015 I've moved to an apartment in Linden and struggled to get TELKOM to move my line. Therefore I've cancelled it online, It never got cancelled, I kept on calling and asking for assistance on their website, AND KEPT ON PAYING. In February 2019 I eventually got a call from a technician, but at that time I was staying on a smallholding that didn't have telephone lines. So the technician told me he'll make contact with the office for them to cancel it. I STILL KEPT ON PAYING! July 2019 the last bill for R116 and because I've paid now for 5 months without using it, I thought there would have been a credit. There obviously wasn't AND THEY'VE BLACKLISTED ME!!!!! I only found out about this last week when I've asked to be pre-approved for buying a property!!!!!