How can I defeat my boss's GPS cell phone tracking on my phone?

I can't turn the phone off and remove the battery. The boss owns the phone and pays the bill but I don't want him knowing where I am 24/7. One solution I thought of was to divert all calls to my own private cell phone and leave my work cell somewhere or place it in one of those 'film safe' bags so it can't pick up the network / GPS. Also I can't hack the software or cause any damage to the phone. Any advice appreciated.