There's a difference between being on an assigned rest period on a trip or as a reserve vs just being "in rest" on your days off. They can obviously call you a million times on your off days, and you can be called and accept a GS/IA that reports in 5 minutes and be perfectly legal. It does get sketchier if you are within 10 hours of a known trip report as far as calling more than once, but as always whenever you are in rest/on off days you are never, ever obligated to answer your phone or acknowledge any contact from crew scheduling.