Quote:
I was unable to find European companies who would sell me a prepaid SIM for an American Cingular phone.


Odd. All I did was walk into a cell phone shop in a mall in Cambridge, and walked out with an O2 prepaid kit. Came with the SIM that worked fine in my unlocked Sony Ericsson phone (from T-Mobile). It also came with a card that was usable at many ATMs to add more money to the prepaid account, and it worked into the Netherlands, Germany and Switzerland with no issues.

Also, unlocking phones if your provider won't is legal in the US under the recent DMCA exemptions.