SPH-L720T stuck on Global??

Hello everyone. I recently bought a few Galaxy S4's to resell. I kept and unlocked one, then sold the others on ebay. One of the buyers just contacted me and told me that they cannot get the phone working on their sprint account because Sprint says the phone is stuck on global mode. What is global mode and is there any easy way I can walk them through correcting it? I dont rememebr seeing a global setting in the *#0011# menu.

Thanks in advance.