Unauthorised airtime transfer - with ZERO solution

I had a look on my vodacom app what my bill for the month is so far. Shocked to see it was R500 more than usual. Looked at the previous month and it was the same high amount. Called the call centre - they inform me that I had transferred R500.00 airtime to someone else. I wouldnt even know how to do this. They escalate my querie and a person from Vodacom calls me back. I inform then that the R500 airtime transfer was not done by me. The number is was transferred to doesnt even ring - I have no idea who that number belongs to. They tell me that someone must've used my phone to transfer airtime. My phone has a double lock. Fingerprint and code. There is no way anybody couldve just taken my phone to transfer airtime. They told me sorry - it could've only been done from my phone. End of story, nothing they can do. This is a bull &^%$ story. It happened straight after my phone upgrade. I want my R500 back PLEASE. I HAVE BEEN WITH VODACOM FOR OVER 15 YEARS. Will never use them again.