Vodacom Poor Service

Hello. My name is Andries Uys. On 2018-03-23 I phoned Vodacom about a account outstanding reflecting on my name at the credit bureau. I spoke to a guy named Mohammed who assist me and told me that there is no account outstanding on my name according to my id number and that he will send a letter. On 2018-03-27 I phoned again and spoke to a lady called Romanie. She also told me that she cannot find anything against my name accept and old account that is already in the archives. She told me also that she will send a letter to clear my name. On 2018-04-04 I phoned again and speak to a lady at the subscibers collection that told me that according to the system no letter was sent to the credit bureau. She also told me that she can only assist me if I settle the outstanding amount on the account. To me it is not fair to hold me accountable for a account that is already in the archives and that is outstanding for almost 13 years. Hope you can assist me in this matter.