Not having a chip at anybody but pilots can be the first to complain 'what are you doing calling me during my rest period or on my day off?'.
OK, sh1t will still happen but at least it will help your rest time to be exactly that, time away from work and not worrying about work.
The regulations stipulate that you need the minimum required rest period, let us say 12 hours, before commencing a duty thus that is the notice period required.
Please bear in mind that the crewing bod does not have satellite navigation as to when you might be in the crew room, he or she is just trying to earn a salary the same as you are so why not just work together?
What's the problem?