Pure frustration

I paid up my account in December 2019. When I checked my credit profile I found that I was still owing. On the 15th of March, I called customer care and was asked to send proof that the account was paid up. I sent the paid up letter. On the 18th of May, I received another email that my account has now been handed over to attorneys because I owe over R17000. Can someone please sort this out.