Exactly! If you are on call, you can’t go to the opera, etc. So, in essence, your job is tying you down and without pay. (See that my response was to SoothingDave who thought extra pay should be unnecessary when you’re given a phone for free.)
Sorry, I thought you may be someone who picks up their phone at the theater!!! It happens all the time. When my brother took his kid to “The Addams Family” musical, he got in a fight with a woman who had an entire conversation on her phone.