they have a separate plan called blackberry connect just for them, those are the only PDA phone cingular has that i’ve never used, so their IMEI’s may be locked but I swap windows mobile and nokia PDA’s and treo’s all the time, including ones that were previously on another account without a problem.
the reason they want you to think they’re locked to numbers is cause I have a regular non-smartphone on my account listed, so I get $19.99 unlimited internet/1500 text messages with a PDA instead of $39.99 for just the internet.