For a digital thermostat: hold in the up or down arrow on the thermostat in your hallway, this will cause the screen to flash. Once the screen flashes it will then allow you to alter the temperature. Alternatively you can remove the batteries from the thermo stat to turn the heating off altogether.
For a dial thermostat: simply turn the dial to the desired temperature.
Please leave sufficient time for the temperature to cool/heat up after you have chosen your desired settings.
You can view the instruction manual for your thermostat here