Ruined credit records while paying

Firstly unhelpful staff when need assistance, then they have ruined my credit score while they were debiting monthly but says I'm months in arrears while paying ,when ask about it no straight answer just people enquiring with finance department but no feedback. It have ruined my credit records I now don't qualify for anything not even a mere cellphone contract ...all I'm asking is to rectify this it's been more than a year before I include my lawyers in this matter. I need my credit records clean