Go into the phones settings and turn it off. Or use usage controls I believe can limit such use that no need to turn off manually. Hope that helped? You can learn about usage controls (they have a new name for it which I cannot remember) At http://www.Verizon wireless.com Good luck
Unless I'm mistaken, there is not a password lock on wifi in the phone settings for the droid razr maxx hd. Verizon's usage controls doesn't retrict wifi, it restricts the data use on their data plan. I can't control my daughter's use of wifi away from home.
I cannot be 100% certain but I believe under usage controls you can restrict the use of using cellular data which in that case I would say you are correct. I would do a Google search to see if what you want to do is possible.