Since you have a T-Mobile variant you should ask in the sgs4 tmobile forum...
However your problem with lte/phonecalls is likely just an APN issue
To further assist we would need to know which carrier you are using the device on
Sent from my SAMSUNG-SGH-I337 using Tapatalk 4
Wanna learn to develop/mod/do cool things? Check out this forum here on xda...its a great starting place full of helpful people! (its where i learned to compile from source :P)
Chef Central > Android