Unhappy [Q] T-moble Note on AT&T service

so i got a T-mobile galaxy note and i wanna use my At&t sim card in it, but im getting really bad service, when i put my friends T-mobile sim it gets full bars 4g, but when i put the AT&T sim in im only geting 0-2 (3 if im lucky) bars, should i use an AT&T modem? someone help