my straight talk samsung grand prime stays in 3g and is slow. how do I switch over to 4g

[AC Question]

My grand prime from straight talk stays in 3g and is very slow. How can I get it to go to 4g?

 

[Rukbat]

What carrier are you on?

When you look at the mobile data signal (on the second page of the battery statistics in Settings), what color is it?