After Sign_on
It used to be once you departed hong kong on a trip.. they own you.Now it is AT SIGN ON...in other words when you turn up for work they can send you anywhere and bring you home when it suits them.
I have flown many times with f/o's on a 4-day(read that as a fly every day)trip to north america who had originally signed on for a 3 hour taipei turnaround.
Once at an outport you are required to be contactable, as you obviously are on Reserve and 'A' days..in fact if you're based YOU have to call THEM the day before!!
They will use any and all means to contact and use you once out of hong kong..and ..if you have a little trouble swallowing this just ask any based or freighter crews how stable their rosters are.
If you're on a 'G' day or outside your standby period or 'A' day then why are you touching the phone at all??