Tell them anytime they call you outside of your shift hours, you will time the call and add it to your final count of hours worked. Keep meticulous track down to the second or record calls if you are allowed to in your state. I'd be careful of how you word it. Maybe send an email that says something along the lines of how you'd love to be a help outside of your scheduled work hours and you'll work with them to create an system to track hours worked from home or OT hours. Until the system is created youd like them refrain from contacting you except through the approariate method in case of emergencies.

Also go to HR about the misuse of your emergency contact.

Wording is really important as they can use this as an example of you lacking "teamwork." If you dont want an escalation I would just go to HR about the emergency contact and "mute" any messages from work.