Your telephone number(s) on your credit card account - keep them current and, when abroad, keep your phone on and battery full [and of course ensure they have this number]
Why?
Because when you spend like a crazy dog on your hols, they see activity far different from your profile and put a
security block on the card and actually
call you
Being cautious, I don't mind this. I think it's better than chasing the Ace, so to speak.
So here's to UBS Card Center and their card-blocking antics
PS: Partner cards and other cards on the same account will still work