Turn OFF cellular radio.
I can't wait for my Moto-G to arrive, so I am winging it here..
You can try this: *#*#4636#*#*, and you will enter the TEST mode.
Select Phone information, and scroll down to where you see the SMSC dialog box, directly above this, you will see another greyed out box with the wording: Turn off radio. Select that, and the radio will be disabled, but will restart on a reboot, but there is a way to shut off the radio completely as well, but this should help for now.
You can also use this: ##7764726(program) and then tap DIAL to access the SPC password menu, where you enter SIX ZEROES, and tap 'verify' to enter the programming menu.
The two you will be more interested in, are the first and third selections, User activation and Extended NAM
You can wipe all the data if you wish (but write that information on paper so you will know its location if you decide to actually use that device in the future!
Scroll down to Extended NAM and write that information down, first to last, in proper order as before.
If you wish to completely disable ALL outbound dialing, you should delete the emergency number listings as well.
To upgrade your overload class, change that number to a '1', so some schmuck can't boot your call in favor of theirs.
Your MIN and MDN should be erased, as this prevents the phone from placing any calls, even 911 calls if you erased those numbers.
You can erase everything, from the SID to the MCC (Mobile Country Code), to anything the phone uses to access the network.
Just write everything down in proper order so you have a point of reference when you forget what you did.
Once you finish your task, reboot the device. You may need to once again, shut off the radio using the *#*4636#*# operation, but each device is unique here, you may not need to do this.
You can then try the above mentioned shut down procedure again, and disable the radio completely.
WiFi should still be operational