I have a Blackberry Storm that is only offered by Verizon. I have unlocked it and am using it on ATT. The best way to do this is to go to www.crackberry.com and go through some of the disucssions there. They have lots of unlocking tips and links. The best one I found was www.berryology.com. This website is all about unlocking Blackberry phones.
If your carrier is ATT as the category suggests, then no! You can get a plan without data and put the SIM card into your BlackBerry. You can do this with any GSM phone. GSM carriers include ATT and T-mobile. If you use a CDMA phone (carriers such as Verizon and Sprint), then you would only be able to if the carrier allowed you to, which depends on the salesperson helping you switch to your unlocked BlackBerry. (Keep in mind, CDMA carriers usually do not allow other carrier's phones on their network anyway).
Yes, BlackBerry devices do require a BlackBerry data plan on Verizon. BlackBerry devices are a Smartphone and they require a BlackBerry data plan no matter what service provider you have. You cannot use them for talking and texting only without Internet or email.
You possibly can since they both require SIM cards. You might have to unlock your Blackberry though to switch services. I haven't a clue which Blackberry you have, but here is a website that might help. http://iunlockblackberry.com/instructions/
You can't use Verizon service on ATT phones or any other GSM phones. Verizon runs on a different frequency, which ATT phones do not support.
If you just want to use the phone and text functions of the Blackberry, then you don't need to, however, if you want to use data, then you should register your phone for a Blackberry service as any regular data plan would not work on Blackberry phones.
No
yes you are charged by verizon
Yes, you can use a prepaid SIM on the phone, if you just want to use your Blackberry Storm for texting and calling, however, if you want to use the phone for data as well, you would need to register the device for a Blackberry Data plan.
Verizon Blackberry
NO
will not work!
You would need to have a blackberry plan if you wanted to use things like BlackBerry internet and messenger etc.