I bought a iphone 3g and it was jailbroken and unlocked with 4.2.0 (i think).

I was having issues so went to go back to 3.1.3 or 3.1.2

Now the restore has taken it back to the original settings and when I connect to itunes it says "sim card is not supported"

I've installed redsn0w but can only make emergency calls.

What should I do next?