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 thermostat to turn the heating off altogether.
You can view the instruction manual for your Towerstat Digital Thermostat here
For Honeywell Digital Thermostats please click here
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.