If it's still under warranty, bring it back and ask for a replacement (or a repair, if they can just reflash the update - which won't remove any of your personal data).
If not, call the carrier's corporate office - it's their update, it broke your phone, so it's their liability. (They'll still have to repair or replace the phone, but you might have to escalate the problem through a few levels until you get someone who understands the difference between "warranty" and "liability" - if they break something, it doesn't matter whether there's a warranty or not.)