Data usage - R2000 after entering my sim into new Phone

My phone was damaged so I entered my sim card into my wife's old phone while on charge and not using the phone I receiced 12 sms messages showing that I have used R2000 of data... although I was not even using the phone. Went to vodacom and they gave me a number to call the accounts department. When I stated my problem the call centre hey said that we will have to pay the R2000. This is unacceptable, I have been a customer for 18 years and if this issue is not resolved me and me family will cancel all contracts at Vodacom.