Total lack of response

My data package expired on 3 December 2015. Coincidentally someone upgraded my package with a handset included on the same day while my access to the service was cut. I reported this to Vodacom when I noticed the additional amount on my invoice on 9 December. At their request I submitted a police certified affidavid stating I had not done the upgrade. Despite numerous follow ups nothing jas been done, the perpetrator has not been blocked and continues to incur costs on my account. Desperate as I have no where to turn next. I keep getting billed for this!