If you are on Sprint and have the Samsung Galaxy S4, there is an OTA update heading your way.
The update is 24MB in size and there is no list as to what the update brings. The current software build for the S4 out of the box is L720VPUAMDC and this update changes it to L720VPUMDL which PhoneArena.com pointed out could possibly be turning on the LTE radio. The thought came from the last letter being changed from a C (Cellular) to an L (LTE). This is not however confirmed at this time. You can manually check for the OTA update under Settings > More > System Update.
Let us know in the comments below if you have received the update yet.
Source: PhoneArena