Not my account

I have now been called a few times by a company ( debt collectors) about my CellC account that i do not have . I have been a Vodacom account holder only for at least 10 years and do not have a cell c account. I was told by the debt collectors that someone must have oppend an account on my name but they can not give me any proof of this. can you please help as when you oppen an account you need proof of res, coppy of id , sallery slip , bank statement and none of this can be given to me . please help as i need to know who it was and where the account was oppend and by who . if the service provider cannot suply this how can they hold me responsible for the account as they did non do their job with the fica of client