Ok, let's clear this up
If you have an o2 Branded S4 then the latest firmware is I9505XXUBMF8
Which was released in August 13, I'd imagine this firmware should enable the 4g lte setting, I can't confirm as I don’t have o2 branded s4.
If you have a stock unbranded UK (btu) S4 then the latest firmware is I9505XXUDMH8
This was released just a couple of days ago. This firmware does enable the 4g lte setting, it appeared as my default setting when the phone booted up (an extra reboot may be required after firmware updates)
How to update?
3 Options here.
1. Wait for OTA (over the air) update to come through, you can check for OTA updates through settings/about device/software update, it will either say you have the latest software and chances are you have. It may also say that the update has reached its max amount and to try again later, this means there is an update but you'll have to wait a little longer to get it, if you just leave your phone and be patient then at some point you should automatically receive a notification to say an update is ready, once this happens just follow the prompts and update your phone.
2. Kies software on PC - Use this option as a last resort if I were you, if Kies says you have latest software then a good chance you do. Otherwise it will tell you an update is available follow the prompts and install the update, I don't use kies myself, it's slow and painful, kies is junk imo.
3. If you lack patience and hate Kies (like me) then go here http://www.sammobile.com/firmwares/1/
You need to simply register for free first before you can download any firmwares.
From that website select the firmware you wish to download, once downloaded flash the firmware with Odin software, job done.
If you are sure you have the latest firmware and you still have no 4g setting then check the following....
You do have an active 4g Tariff.
You have a 4g Sim card.
Try rebooting your phone again after completing any software updates.
If you meet all this but still don't have any 4g setting then I can only suggest you contact o2 who possibly haven’t enabled something correctly.
