Unhappy client

A few months ago my account was debited 3 times by Vodacom - all those debit orders were not authorised by me. A few days later i was contacted by a callcenter agent informing me that myaccount is in arrears. I then went to a Vodacom store to enquire and was informed that "I took 3 iphones from Vodacom" I have never had any Vodacom contract phone except for a modem of which i was paying R40.00. I recently checked my credit record and it shows that im in arrears with R3800. I would like this to be sorted out asap by Vodacom as its negatively affecting my credit record. I would like to know who and how were those transactions authorised using my personal information and banking details...feedback would be appreciated.