The Operating System software can be installed, but it will be up to Alltel as to whether they will activate a Sprint device on thier network. As they are now part of the Verizon family, I don't believe that they will. You may want to give them a call to find out for sure.
1st Step in Troubleshooting: Do you have a BlackBerry Data Plan?
2nd Step in Troubleshooting: Pull the Battery.