I have alltel as my cellular plan. There is a phone on ebay (Samsung Delve R800) that I want to buy, but it says that this is a U.S. Cellular phone. (I've noticed that they sell a Samsung Delve R800 for alltel also, but it's not as cheap that's why I want to get this one :P). If I buy it can I still use it with my alltell plan?

Well if it has a sim card and your phone has a sim card then yes you can.All you do is take your sim card out of your phone and put it in the new phone and your all set to go.