Unhelpful and bad service assistant and

I had a steady engine on and a sudden loss of power this morning. I call the service centre in Kempton Park where I usually service my car, and the service advisor tells me they are fully booked. As a breakdown is different from a service booking, I emphasise she forwards me the service manager. The said service manager was already very agitated and unfriendly, telling me he can't help me as they are fully booked, and they will get to it when they get to it. Not even a suggestion of what pre-checks I can do or alternatives.