Comment by tim333

I don't think it's down to the SIM. It's more they call help at the phone company and say "hi I've lost my phone, number 0123123. Could you transfer it to my new handset with another SIM in." Or similar. I had my one (with Three UK) transferred to some random fraudster this year. I got it back but it was a pain and potentially dangerous. In fairness to Google they didn't manage to get in to that.

Suggestion to phone companies: When receiving such requests email and text the user saying "we've had a request to transfer your number, contact us if not you" rather than just cracking ahead.