Jay, you can look at your Options > About to see what the OS version is you have. It won't say "Alltel", but the OS version number should tell you that your OS upgrade loaded.
But you don't need Alltel's OS to operated the device on Alltel... it will need unlocking from Verizon. I just am not familiar enough with Alltel to know offhand, some CDMA network carriers like Verizon will not allow other devices purchased from other sources on their network. How do I unlock my BlackBerry? - BlackBerryFAQ