If i unlock my sprint blackberry phone will it work with an other carrier?

I have a sprint blackberry but the bills is coming up way to high due to taxes!,so i wanted to know if i unlock it would it be able to work with Wal-Mart new service STRAIGHT TALK? my brother-in-law had sprint service and and switched his number with STRAIGHT TALK with any problems but he bought the a Straight talk phone but i want to keep my blackberry cause i haven't even had for more then 4 months!! i really don't care if all the application don't work as long as i have unlimited text ,internet access and no high bills am Good thanks

Any question needed to be answered to have a more accurate answer are more then welcomed!