Boucharda - we also have Galaxy S8's through AT&T. WiFi calling works beautiful just like you said. Ya just have to try it, and once you do, you'll never worry again about SIM cards, unlocked phones, type of cell service, etc, etc. Totally hassle free. If wifi calling isn't an option on your phone, there are several free wifi calling apps that people say work great.

We do have AT&T International Calling set up just in case we ever need it, but in last 5-6 trips abroad, we have never needed it. We do use it occasionally when wifi is un-secured and I wanted a more secure wifi connection and used my phone as a hot-spot. I strongly believe many people need to consider that A LOT since anything on your phone can be copied in nano-seconds on open wifi. Many people don't even realize how many of their passwords are stored on their phone since they often don't need to be re-entered after you've used them the first time.

We used that ATT International plan before we found out about wifi calling and it always worked great everywhere. It's just a one-time setup that takes a minute and its there forever. Sure, it's $10 a day for the day you need to use it, but that's the cost of dealing with whatever emergency or critical situation arises. For us, other than the security of a personal hot-spot, it's just a great back up as a just-in-case.