How to stop an iPhone getting blocked?

I'm thinking of buying an iPhone from EB games, or off a person I know. I'm just wondering if there's a way I can stop it from being blocked after I hand the money over. Can I call Telstra, or another provider, and tell them what has happened, and change all the details to mine.

I'm just worried about buying one, then it being blocked because it was "stolen" or something.

Added (1). I'm not planning on buying a stolen iphone at all, but there are people out there that I know have sold their own iphone to people then for some strange reason report it as stolen.

Added (2). If I bought one from EB games, I don't really see how I'm meant to know the previous owner, and that would mean they could block it without me knowing, and I could be stuck somewhere without being able to use a phone…

Buy from a source that does not sell stolen phones. If you buy a stolen phone, you have nothing to complain about.