You will have to know the MMS server for Alltel, I can't help you with that one I am afraid. This thread
http://forum.ppcgeeks.com/showpost.p...56&postcount=3 has the registry edit you would need to do to edit the server.
On a side note, what made you think that a CAB named PPCGeeks
SprintMMS would work for Alltel's MMS system? Even if the Sprint server would work for you, the PPC access to the MMS server at Sprint has apparently been removed, so it won't work for anyone at the moment anyways using the Sprint address.