Samsung Galaxy S5 — Cricket stuck at 5.0 on wife s5 any loophole

Ok thanks either way. It's a cricket g900az and won't update and I can't fund romantic that's higher than 5.0 . Now I know cricket is g900a but not sure of firmware is marsh yet and is the cricket unlocked and bootloader unlocked to work? I'll do firmware . Thanks if u can give me what I need to do than I'm good. I use odin for yrs and did other phones and I own s7 edge g935f unlocked international lol I change every other day. Waiting for nougat thanks

Also wanna say I tried to remove sim to see if it would update. It always said no but it said yes. It said stuff like normal but a 0kb in 2 spots. It took 10 minutes. No change in a anything but maybe the security file but nothing else. Put simply in and fine.