Life isn't fair I guess. I don't have a problem if that is expressed clearly to people, but I have yet to be able to find anything warranty documentation that states leaving your carrier and/or unlocking the phone voids the warranty. If this is in fact true, shouldn't this be clearly written somewhere?
Outside of the T-Mobile booklet that came with the phone, I have only found this (PDF): http://www.blackberry.com/legal/pdfs...es_English.pdf
In both the warranty booklet I got with the from, and in the above PDF, I see nothing that even implies your warranty is void if you unlock your phone or change providers.
I have no problem accepting something that I don't like, but from what I can tell this appears to be nothing but fraud.