As I said above, just nuke the antennas (a box cutter through the antenna leads is usually enough. If you're really paranoid, short the lead out at or near the equipment end (as near as to the feed IC as is possible).
I do this on old smartphones that I have no intention of ever using as a phone again (say for testing APS etc.). It's dead easy, a razor blade through the circuit board tracks that connect to the antenna(s) and it's all over—no phone, with or without SIM (i.e.: no emergency service) and no WiFi or Bluetooth.
