In some companies, a culture of “always on” has crept in. People are getting emails and phone calls in their spare time.
As a solution, add this to your contract: For every minute you spend on work related tasks in your spare time, you can log twice the time in your tracker. Tracking happens in 15 minute increments.
So if someone really needs to call your during the weekend to ask just a quick question, you can leave half an hour early on Monday. And if that question turns into a 4 hour monster, you have a whole day off (or eight hours overtime).
That way, there is a “price tag” on your spare time. People don’t have to feel that guilty for calling you but they are also aware of the cost when they do.