Help Slow Internet

[Nate12]

Hey guys, hoping maybe you can help me out, my wife just bought an exhibit through t-mobile and the 4g is really slow, she is getting 400kbs and when I test the 4g on my galaxy s4 it's over 3megs, why is her phone so slow? I know her phone isn't as powerful but shouldn't it still be just as fast Internet wise? Also her battery dies super fast like a couple hours and all she does is text during her work hours, thanks for any help.