What if the heating valve is turned off? Can I ask the plumber to open it?

Go directly to the heating company or property.

If it is closed by itself, find a wrench for the ball valve and turn it for half a turn. If it is a plunger valve, turn it counterclockwise. If it's not bad embroidery, use some force. It doesn't matter if the valve is closed, just close it tightly. If someone else closes it, they will find a property and heating company to solve it.

Heating valve only refers to an accessory of radiator system, which is a kind of valve. Commonly used heater system valves in the market are mainly divided into: gate valve, ball valve, safety valve, balance valve, stop valve, pressure stabilizing valve, pressure reducing valve, electric regulating valve, etc.