Can you please help me figure out the problem? Urgent!?

My air conditioning will not turn off no matter what I do. I turn it off, I turn it up, down, try to program it. IT's been going on for HOURS and not only is it freezing, its loud and I can't sleep. We had a plumber messing around today in the area where the unit is located in the house. I went down there and couldn't find any switches to turn it off. I have two main questions: 1) We don't have Carbon monoxide detectors that work properly, and I'm feeling dizzy and dissoriented. Could the constant blowing and malfulnction cause CO in great amounts? 2) Can I simply break the circuit in the fuze box and leave it off until a technician can come out here? Help- I;m already sleep deprived and I'm too nervous to sleep.