Root galaxy mega 2 g750a

I have been trying to root my att galaxy mega 2 g750a for days and I can't win. I've try ed everything from Odin, to king o, chainfire and a lot if other methods and I get the same thing every time....the file bin for su doesn't
exist, normal and alternate locations, no busy box...shell user....it's frustrating.. can anyone help me with this please....
Thought about changing the shell user...but...that's a little more complicated, and I hate lollipop, I turned the phone off and kiktkat was gone.