what plan are you on?

any error messages? please provide me with other details so I provide better information to the customer service 

hi there 
are you on the go at that time?
welcome to the bandwagon 
mind telling me your phone model?
and, just a few days of inactivity, and this thread has been moved to Telco talk(new subforum) 

probably that your phone does not support the band that u mobile is using (2600mhz). If you wanted to know then you have to search which variant of S4 that you're using.

wah...

try to flash EMJ5 radio and see... coz this morning i also encountered w this MKF radio..==!

call also kenot..

probably that you've flashed the wrong baseband, disabling your ability to connect to the 2600mhz band. Anyway, go to the S4 thread for more help 

which telco did you got it from?

I mean your S4 la 

I know that it is from UK la, you've mentioned it before. I want to know which telco from UK did you bought it from so I can identify the variant of your S4 la aiyo    (trying to help pun susah  )

  then probably try and contact Samsung UK via facebook or twitter(I think they should be more responsive than here) and hopefully you can get your answer.

If you want to save the hassle, sell the phone and buy Lumia if you don't want to choose(it has support for all major bands that we're using), or a phone that is listed at U Mobile's site that has LTE support

Z1 looks nice, although the camera is a bit suckish as so to say

get Nexus 5 lo..

You can get some reviews at the Nexus 5 thread, although I feel that it'll be biased though https://forum.lowyat.net/topic/3117491