Appointed panelbeater constantly extending deadlin

I am unsatisfied with the consistent extension of the deadline to complete work on my car. Each time I call the panelbeater they give a new deadline. I need to make apointments with work clients & unable because the panelbeater can not give exactly as to when I can get the car. when I called this morning they said it wont be ready by Monday which was the latest deadline they gave to the insurace.