Iphone won't sync to itunes, no sim?

So I have an iphone 3g that I've been using an ipod (no sim!), Itunes won't let me sync my iphone to it, because it keeps asking me for my sim. Is there I anything I can do to get rid of this problem? Can I put my own sim card in it just to get past it asking for my sim card without At&t charging me like crazy?

If you have a att sim, turn off 3g in iphone settings, then pop in your sim to get past axtivation screen.
if that doesn't work, jailbreak it.