blacklisted wiothout having an account with cell c

I was applying for finance with standard bank, only to find that I have been blacklisted from CELL C, I owe ,them R2500 or more, but I have no accounts with cellc, called the contact center they cant pick up any records using my ID, then how do you blacklist someone. called their legal department several times and I cant get through. very frustrated because im been inconvenienced