I get a flat rate per week/day that is basically the same I would get paid for one hour of work, per day, whether I work it or not.
If I go out onsite, I get three hours of OT minimum.
But I do work for a larger company, when I worked for a smaller, unionised company, I still had the flat weekly payment that equalled an extra hour per day, and then paid from the time I left my house until I arrived back home again, if I went out.
There was something for phone support, but most of the time the phone calls were so short I didn't bother trying to get any moeny out of it, it was a company supplied phone, and I had that 7 hours of pay for the week anyways.