Upgrade done on my phone without my permission

I picked up in an increase in my debit order in the last 3 months on my vodacom account. I called vodacom on the 28th April to report the matter. I was asked to fax a copy of my ID and affidavit saying that I didn't upgrade my number and didnt receive a new phone as claimed by them. I have not received any form of explanation or feedback till this day. This week I was told to wait till the 8th of May for a call. Still no call untill i called them. They tell me tha case is closed due to frawd but i need to know if I will get a refund for all the months they debited an extra amount. Please help.