Can a at&t iphone 4s be activated on alltel?

The phone is unlock and has no sim card and dpi you think Alltel will put their sim card

Yes,

As long as your phone is unlocked it can be activated on any company that accepts sim cards.

If its really unlocked, it will work. There's a simple way to check, when you restore the iphone in itunes, you will see a "congratulations, your iphone has been unlocked" message.

How can I unlock my iPhone 4s from alltel? I purchased from someone and straight talk can't