This is one of those questions I'm asking from the point-of-view of 20/20 hindsight.
When it happened to me the other day I panicked and ran away from the guy.
Even at the time, panicking and running away seemed like the wrong thing to do, but it was like that one time at Thanksgiving where I forgot to buy cranberry sauce and it was the only thing I was supposed to bring to Thanksgiving but 7-eleven doesn't sell cranberry sauce and if you take cherry Slurpee and add some shredded beef jerky to it to, well, to thicken it, it doesn't taste much like cranberry sauce.
Or so I was told.
I hate cranberry sauce so I didn't try it.
So you're standing in a crowd and some stranger asks to borrow your cell phone . . . eh.