I found how to enable LTE (4G) throught the service mode without any rooting, or software modification.
select the dial pad and enter *#0011#, wait and you will see the Service mode common window.
Press the pouch button on the lower left and select BACK.
Press the same button and select KEY Input, enter Q0000.press OK and WAIT(up to 1 min).
You will see the MAIN MENU window.
Select UMTS-->Debug Screen-->Phone Control-->Network Control-->Band Selection-->Automatic
Done.MAy be restart the phone.