Supposedly Tmobile's "extended range LTE" is better in rural areas/inside buildings...but it "band 12 (700mHz) and the iphone 6 doesn't do that...who knows...I have to try something.
I just upgraded from a 4 to a 6 and there is no improvement in signal strenth/service. Going to have to try another upgrade to a band 12 (700mHz) phone.