Newbie + quick question

I recently bought an unlocked tab s 10.5 att variant (i'm on tmobile). I tried to update to lollipop but it's not available. Is there anyway I can still update to lollipop without rooting? Or is rooting + flashing my only way to get lollipop? thank you for your help

edit- oops, please move to Q&A, accidentally posted here in general section