is your phone officially-unlocked set or locked? if it's locked, you will need to jailbreak with redsn0w, and install ultrasn0w to unlock it. read the first page for more info.

it's okay. it can be done. just re-jailbreak with redsn0w, install Cydia only and download ultrasn0w. further instructions and guide on jailbreak can be found here.

it's okay. it can be done. just re-jailbreak with redsn0w, install Cydia only and download ultrasn0w. further instructions and guide on jailbreak can be found here.

since your phone is a locked US set. it will need an AT&T sim to activate it aka access into the phone.

but you can activate it via redsn0w. that's why you'll need to re-jailbreak. follow this guide.

once you've done so, you'll able to access the phone, but you can't access your Celcom network yet since it's still locked.

that's where you'll need to download ultrasn0w from Cydia to enable the phone to be used with Celcom or any other network other than AT&T.

you don't need to do that. here's what you need to do:

1. Download iPhone 3G 3.0 IPSW from here.
2. Jailbreak with redsn0w, follow the guide here. (install only Cydia)
*when asked to select firmware, select the 3.0 one
3. Download & install ultrasn0w from Cydia, guide is available here.
4. Reboot and you're done.

jailbreak it with redsnow n  download ultrasnow from cydia to unlock it...