My recommendation would be to go to the place where your stepfather got the Blackberry (hopefully he got his next blackberry from them too) and ask them if they will unlock it. Unlocking over here is costly (I was quoted 30 pounds to just to unlock an old cheap Samsung I brought from home). I've had people unlock them for me for free in the States when I got my plan from them.
Where did you go to get your phone unlocked? I got my old UK mobile unlocked over here for about £10. If you go to a retailer (ie T-Mobile, O2, Orange etc) they'll charge you an arm & a leg. If you go to a market stall / specialty mobile shop (ok, admittedly they may look a bit shady compared to the nice mobile stores in the US), but they'll do 'em quite cheap. Otherwise, you may want to look into doing it yourself online.
DH had a Motorola he unlocked himself all he needed was his data cable (which came with the phone) and bought an unlock code online.
Personally, before going anywhere to unlock it I would do an internet search on the model regarding unlocking it. You may just get some good recommendations on places to go as well as if you might be able to buy the code & do it yourself...
Good luck!