If the heater blower fan inside your car will not turn off, then first thing you should do is turn off the ignition. This will cut the power to the heater blower fan and will stop it from spinning, as well as putting a stop to draining power from the battery in your car. Every heater blower fan has a heater module, this controls what the fan does, if this is faulty it can cause the heater blower fan not to turn on or off. Replacing the heater module is guaranteed to fix a heater blower fan that won't turn off because i had a car with the same exact problem and it worked for my car.
You might not get access to a heater module replacement part for your car straight away, so for a temporary fix if the heater blower more is still working, even when the car ignition is turned off, then locate your car's user manual and locate were the fuse is that protects the heater circuit. Once you have found were the fuse is located in your car, simply remove it from the fuse box, this is to turn off the heater blower fan, as pulling the fuse out breaks the circuit. When you want to use the heater blower fan, simply replace the fuse.