Vodacom Unauthorised Debit Orders (4 months)

I have been receiving unauthorised debit orders from Vodacom for 4 months now. I do not have any cellphone, data or wi-fi contracts with Vodacom. I initially thought nothing of it and reversed the debit order and placed a stop payment on R90 something debit. Every time they debit I did the same thing, but this amount has now gone from R90 something to R600 something. What next? Can someone from Vodacom call me so that we can establish how they got my account details, who authorised them to debit my account, and for what, and for the unauthorised debit orders on my account to be stopped. This cannot continue.

Regards, Reinard