You mean debrand as in... unlock it from T-Mobile or someone? That's easy - you just buy an unlock code for that. I did it (UK T-Mobile T303 Daisy Edition).
Company I used was fonesunlock - you just send them your IMEI and 20 quid and they send you your code back.
There's instructions on their web site - but when it comes to entering the code you get down to a choice of two keys to change. I think you change the second one, which is the network lock applied by the mobile operator. I don't think you can change the first one anyway, but I'm pretty sure it was the 2nd one I changed.
It was all pretty painless and they were very good at responding to my e-mails. You could just send them an e-mail. The guy's name was Tim.
All I need now is someway to add the Russian language to it. I'm a bit long in the tooth to want to even read about doing anything drastic to the phone. If there's a file I can download and bluetooth it over to get Russian on, that'll do me. "Flashing" meant something else back in the good old days.