Bad treatment

Sheet street hasn't lived up to their standards of doing business, recently I had checked my credit score and found out that I am in arrears. To my knowledge I had my debt settled with sheet street, so I went enquire about that. I was told I had joined some insurances, which I don't remember giving them my consent. I paid up an amount of R250 and I asked them to cancel all the policy which they say I joined. Yes I did sign a cancellation form, but just a month ago when I re-chek my credit score I still found that I am in arrears with an amount of R300. I went back to sheet street and asked them to cancel the insurances which they say I had joined, I was told they can't cancel before I pay the R300 which I paid and sign the same cancellation form I had signed months back. I am not happy with the way they have treated me, they are not trustworthy at all. My credit score is bad due to their carelessness