If you have a Honeywell Thermostat, then there is a chance to enabled security lock settings. Once enabled, you or any other user must enter a four-digit password in order to make changes.The security settings on your Honeywell thermostat can be used to prevent unauthorized changes to system settings.

Enable lock security

1: Press the "Menu" button on your Honeywell thermostat and press over until you reach "Screen Lock" then hit select

2: Select the lock option to use

1. Select "Unlocked" if you want to allow unrestricted access to thermostat settings. 
2. Select "Partial Locked" if you want to allow other users to change only the temperature.
3. Select "Fully locked" if you want to restrict access to thermostat settings completely.

3: The screen will then display a pin that will be used to unlock the thermostat

4: Hit Select, then "Yes" to confirm the lock settings