I'm from Canada and will be going to the states for a week, if I unlock my phone and use BBM or text how would it be different from a phone that is locked to a phone that is unlocked
but where does my bill go to / do i need to go out and buy a AT&T sim card how does it work, sorry for sounding like a tool, I have no clue how this works
In order to avoid big roaming charges from your home carrier, you would need either an international data plan from them, or you would need to get a local SIM that includes BlackBerry Data.
Currently, AT&T in the US does not have BlackBerry Data on Pay as You Go or prepaid. TMobile does, however.
would I just go to a Tmoblie outlet and purchase a sim card?
Yes correct, you can purchase a local prepaid SIM card when you get to the USA. Unlocking your Blackberry will enable you to use it with another SIM card. Leaving your phone locked will only work with Rogers SIM cards.
If you get it unlocked, you can go into a Tmobile or AT&T store/booth and get a sim from them with some pay as you go credit. I'm not sure if any of the American carriers sell BB data packs on pay as you go though. You should probably try that before planning on being on it all day while you're in the US
However, its still smart to get your phone unlocked regardless in case you should ever be in a position to sell your phone, use it in another country, or change carriers in Canada.
The experts there will answer all of your questions 
