Another option, if you can't get IMS to work, is to download the Verizon Messages+ app while you're still in the US because it needs to text your Verizon line a validation code as part of the setup. But once it's set up it lets you receive and send SMS messages as well as call, using your Verizon number via whatever data connection is available. You can also install it on a tablet if you want that functionality on your tablet.