" my plan would be stop paying , mak sure the machines arnt externally facing "
In other words, leave your machines vulnerable to attacks from compromised systems inside your firewalls.
This is one of the primary attack vectors exploited by Wannacry and a number of other worms. It's that level of complacency which _allowed_ it to become so successful.
One of the maxims of retail is that your largest stock theft threat comes from staff("shrinkage"), not shoplifters, with spoilage coming a close second (also mostly caused by staff) and it's something that people seem to forget in their focus on external threats. Those threats still apply in non-retail business, just in slightly different forms.