"I got called from my assistant and office"

It's not a clear and grammatical English sentence. Perhaps what is meant is I got a call from my assistant at the office. or I got a call from my office assistant.

It’s a little weird sounding out of a context, but yes it means what you suggested. Think about it like “I got called from the other room” (like “someone yelled out to me from the other room”)

It's unclear. I'd guess they meant their PA and someone from their department, probably their boss.