Duplicate and ********** sale of account

My Cell C Account has been duplicated and sold my account to the Nimble Group without my knowledge 4 months after I paid the account up I received a incorrect paid-up letter with incorrect ID number and Account number I Questioned it and received a correct paid-up letter a year later last month I Questioned my credit report and got feedback today where the credit bureau attached a statement from the lawyers (Nimble group) showing I owe the lawyers money even after I attached a paid up letter from cellc with the same account number as the nimble group one but the nimble group reply to the credit bureau is they don't know why a paid up letter was issued to me I have proof of payments I have incorrect paid up letter and the correct paid up letter but still I'm in the wrong can anybody help me please