Default unlocked mega question

1) I noticed in the lock screen it comes up TMobile. It also comes up Tmobile in the pull down notification bar. How can I change it so it says ATT instead? My phone is rooted. This is the i527

2) I get lte coverage and a icon comes up that says 4G and it says LTE underneath it. How can I change it so when 4G comes up (when on hspa+) I have it say 4G underneath it say H+?