Just a weird question; do you have your two cable boxes really close or in the same room? For example, your PVR is attached to your modem but you have a cable box to your TV across the room. Since the remotes are IR and not bluetooth; you could be controlling both boxes. So if, say, you click on your box - your PVR could be ordering everythings.
I'm confused about the box you are calling PVR/modem. There is no such device. It's either a PVR or a modem, not both.
What is the model number of the device you are calling the PVR/modem that's not attached to a TV?
Are the unexpected recordings live or scheduled for the future?
I recall reading some posts here about similar situations. It's possible someone else's PVR is cross connected to your account at the TELUS back end.