Making an emergency call does not even require a sim card or a roaming agreement between your home network and the networks of the visited country. As long as your mobile device is compatible with the mobile networks in the visited country your phone has been designed such that even if you have no other services or your services have been disconnected by your service provider you’ll still be able to make emergency calls. All you need to do is make sure that when your travel your mobile device is 4G and VoLTE (Voice over a 4G network) compliant. Most mobile handsets manufactured after 2015 are, but its always best to check with your provider.