I found the 'import sim contacts' button the other day, and foolishly pressed it without thinking. Next time I looked, I have s***loads of some other person's contacts in there – maybe around 100 or so of them. I eventually synced to gmail and deleted them that way (a lot easier!) but now I am paranoid about having somebody else's SIM. I bought the phone new, and the guy in the store said he would give me the sim 'for free'. He didn't tell me that it was a returned one, if he had I would have said I'd rather pay for a brand new one.

What I'm concerned about now is, is there anything else to do with this SIM I need to worry about? Should I go back and buy a brand new one, or doesn't it really matter?

The rest of my service has been fine with the MAJOR EXCEPTION of Vodafone changing my plan randomly without authorisation. That is an ongoing saga and a very long story. But I wonder if that plan change had anything to do with me having someone else's SIM?