On call, off call

[Madness1]

I am curious about something.
On call means that a person is not working, but is available to go to work if you contact them.
But what about the phrase "off call", as in not available to go to work, the complete opposite of "on call"?
I have never heard of "off call", and I don't believe it exists, but perhaps I am wrong and you can actually say it?

 

[emsr2d2]

I would use it only to refer to the end of a shift on call. My aunt (a haematologist who was regularly on call overnight) used it.

Helen: Are you working today?
Sarah: I'm at home but I'm on call.
Helen: What time do you finish?
Sarah: I should be off call by 7pm.

I wouldn't say that you were off call on a day when you're simply not on call.