Well, not in CAP 371 of course, it is part of our CLAs. However as far as i know there is absolutely no rule either in CAP 371 nor in EU-OPS that you have to take calls from the company anytime you are not on call out duty. Therefore i wouldn't take it anyway and just turn up on time for my planned duty.
But alot depends on the working laws that are applicable to you and your employer, company culture (do they misuse SIM checks to fire pilots?) and so on.