Vodacom ********ly updating my credit profile even after account is closed.

I signed a contract with Vodacom back in 2015, a decision I regret to this to this day. My contract ended last year, I had to fight with Vodacom to get a paid up letter. They eventually sent me the letter and the account was closed, however Vodacom continues to update my credit profile that I am defaulting on monthly payments. As it stands they recently updated my profile that I am 150+ days behind on payment. How so? My account has been closed long ago,a paid up letter has been issues, I even ported my number to another provider, yet they still damage my credit profile. I would like to take legal action against them, and sue them for ********ly tempering with my credit profile even after the account has been closed. I can’t buy property because my credit score has been affected profusely. Please advice on the steps for legal action.