Prepaid SIM for 3G data in US - is it possible?

[Guest PDADoc]

I work with a European pharma company and frequently travel there. As such, I have an account with T-Mobile in Germany which allows for smooth 3G while in EU. I've used it in the US, but the roaming charges are just too prohibitively expensive for it to be a viable option.

However, I'm an American and live in NYC but have an account with T-Mobile, which does not yet have that service here. What I wanted to know is this: is it possible to purchase a prepaid SIM from Cingular and use that for 3G data without too much hassle?

I got a Cingular GoPhone prepaid SIM that's a 3G one (at least it says so on the back) and thought I'd be able to use it that way, but while I get the "U", whenever it tries to connect in a 3G area, it promptly disconnects. In EDGE areas, it connects and works fine. Tried to deal with Cingular customer service, but that proved to be an exercise in futility. :rolleyes:

Any ideas? :(