I have two phones, and usually just put the one for the country Im not currently in on a charger and hide it away in a drawer, and take it out only when Im packing to go to the other continent again.
The Canadian phone usually gets 50-100 spam messages and missed calls during the 2-3 months Im not using it.
The Czech phone has never had a spam message or missed call on it ever.
I dont see why strories like this would have no bearing on this discussion. Its relevant, anecdotal evidence.