There’s 2 ways around this issue...
Don’t answer the phone if you don’t want to work OR When you see your not scheduled, submit a 3971 Leave Slip for your appointment.
As others have stated you’re confusing being available with being on call.
“Repeated unavailability” does not mean, nor has it ever meant, an expectation that employees wait by a phone for a manager to call.
If the people in your office don’t want to exert their rights I understand; but please stop pretending some lunatic’s policy has any contractual basis whatsoever. It doesn’t.
