Open your phone’s failed and start typing this code*#*#4636#*#
On running the above code you”all land into a testing screen where you will see four option phone information,battery information,usage statistics,and wi-fi information.
Click on “phone information”
Scroll down until you see ‘set preferred network type.’
From the preferred network type,select LTE/GSM/CDMA auto(PRL)
Now,scroll down and hit the update button.
Now your phone is 4G capable.if there’s anerror while updating try choosing another network type whichhas the lte option.