INCORRECT SURNAME

I have been in touch with Vodacom telephonically and have sent numerous e-mails in order to change my surname. I have also on numerous occasions sent through all the documentation needed with NO LUCK of my surname being changed. This is very frustrating as it is inconvenient to constantly fax my documents through and I need the details to be correct as I use the billing for proof of residence and my surname is always a problem. I have been married for over 6 years now and have tried to get this sorted ever since. I would appreciate assistance in this regard.