Verizon Galaxy s4 to T-Mobile

Hey guys new to this site,

My mother recently switched to t-mobile and is in dire need of help. I did the general apn settings for t-mobile's let network but lte works in few places and she is unable to send texts. I heard there is a way to add lte bands to your phone but a root is necessary.

I am currently on lollipop 5.0.1, is there a way to unlock the bootloader to root the phone?

Thanks in advance,

James