How can I unlock an iPhone 3G that no longer has a service plan? I have an old iPhone 3G which I purchased in Canada and it was locked for three years to Rogers, a service provider. 

Last month, I stopped the service and moved to the US. I was not able to use the iPhone because it was still bundled with a Canadian service provider and could not even go into the operating system. 

I called the service provider but they won't help me unlock because I've stopped the service. 

What can I do now?
The programmer chpwn has created a web site where you can see if you can unlock your iPhone at http://caniunlock.com. Look there, and also at http://jailbrea.kr for jailbreak information. Good luck!