CellC is messing up my credit profile and life

I had a contract from 2007 .. due to financial problems I could not pay my account regularly. My contract was terminated in 2017. In August 2018 I paid up my outstanding balance with NuBebt. I received a paid up letter and a zero balance statement. I struggled to get my profile updated as such. In March 2020 after contacting all ITC houses the account was updated to zero. To my amazement, this month I was approved for desperate funding I needed, when I went in to sign, I was declined because of a "debt I did not declare" .. which was a listing from CellC with a new balance and 3 months unpaid listing. This really messed up my life I don't know what to do as I really can't get any financial help due to a CellC account I don't even own. My efforts to sort this matter with CellC and NuDebt is forever failing. At the Centurion branch they told me they cant help me as the account with legal services. I'm angry and frustrated.