Unlocked but no signal

[clouse123]

NEWB to iphone and this forum. Purchased a 3G through ebay. Seller claimed is unlocked but with TMobile sim it will not work. How can I verify it's been unlocked? When I connect to Itunes it states need to be updated but when I try to update it does not recognize the Tmobile SIM and will not proceed. Should I even try to update. Currently is 2.2.1. Any help is appreciated. I'm not a moron, but not a computer wiz either. A nudge to a good tutorial is much appreciated. Thank you in advance.

[radack1155]

NEWB to iphone and this forum. Purchased a 3G through ebay. Seller claimed is unlocked but with TMobile sim it will not work. How can I verify it's been unlocked? When I connect to Itunes it states need to be updated but when I try to update it does not recognize the Tmobile SIM and will not proceed. Should I even try to update. Currently is 2.2.1. Any help is appreciated. I'm not a moron, but not a computer wiz either. A nudge to a good tutorial is much appreciated. Thank you in advance.

Make sure you turn off 3G
Settings - General - Network - Enable 3G Off

[clouse123]

Turned 3G off. Now get very brief display of "invalid sim" then nothing.

[radack1155]

Turned 3G off. Now get very brief display of "invalid sim" then nothing.

I would go ahead and update to 3.0. Use Redsn0w to jailbreak, and unlock using ultrasn0w. It's very easy, I had no problems.