If I have cell phone service with Alltel, can I buy an "unlocked" phone of any kind and have them activate it?

Answer 1

No, not of just any kind. It will have to be a CDMA phone, preferably dual band/tri mode as most are these days. Most CDMA phones like those that come from Verizon are unlocked anyway. The exceptions would be Sprint PCS and their MVNO's (i.e. Virgin Mobile) and Revol (and the like), but if the person selling them has the unlock code or changed it to all 0's then you can use them.

After that you will have to somehow get the Alltel PRL onto your phone otherwise you will be roaming on the original carrier's towers all the time. Sometimes you can do this with some creative OTA programming codes, i.e. *22801, *22802, etc. until you get the OTA message from Alltel. If the phone is a model Alltel carries, a store that has a service department should have equipment to do a PRL upgrade there. It can be done!