In Google Voice, go to settings, make and receive calls, prefer WiFi and data when traveling internationally to prevent unexpected cell usage by GV for outgoing calls.

I used Hangouts to avoid using my cell number prior to Google Voice adding the prefer WiFi and data option when traveling internationally.

Yeah, I figured out that setting a while back, but since it's not an everyday drill, I didn't recall the details, which are pretty simple to find online. I just wanted to alert others to the existence of this setting.

You need an iOS device with no number active. Turn the iOS with number off then make a call using the app over WiFi to create an iOS without a number for your device. The other iOS listings are for your previous iPhones and can be deleted. I have the linked number iOS and the iOS for the device.

Wi-Fi calling is enabled. I did need to ask Consumer Cellular to enable Wi-Fi calling, but there was no push-back at all. (There's a bit of a nomenclature problem here, as "enable Wi-Fi calling" required Consumer Cellular to "ungray" the switch in Settings so that I could turn it on, and it seems awkward to say "enable enabling Wi-Fi calling".)

WiFi calling is an add on Apple feature licensed to the cell provider for calls and texts to be sent and received when the phone is not connected to the Consumer Cellular cell network. Not all cell providers license the feature and some restrict the usage. WiFi calling is required for IMS.

I am not certain how Android licenses WiFi calling but my Pixel and prior Samsung phones are enabled for WiFi calling.

You can use the T-Mobile DIGITS app to send/receive calls over wifi while overseas. You just need to make sure that your account is provisioned for DIGITS (which may incur a monthly fee, which I'm sure you can cancel after you get home). I'm on such an old plan that DIGITS was included. The other perk is that you can install DIGITS on your tablet as well as use a web-based version on a laptop, too.

And a warning/FYI... while you can send/receive text messages on the DIGITS app to/from regular phone numbers, you will not receive any two-factor authentication text messages.

After reading about digits online, I was concerned that once you provision your number to digits, it’s there permanently and can’t go back to your SIM card

Definitely not the case. Think of it as T-Mobile's version of Google Voice using your T-Mobile number--or you can pay a monthly fee to have a totally different phone number that lives only on the DIGITS app. In fact, I can use the DIGITS app on my tablet (wifi-only), and I can set it up to run all four lines in my account. If I wanted to, that is. I just enable DIGITS on each phone (you need to keep your T-Mobile SIM card in to receive the 2FA text message), then I insert local SIM cards in each phone, and they're good to go. When I swap back to our T-Mobile SIMs, I turn off DIGITS on each phone.

If you have T-mobile, your incoming SMS should be free, and I believe is NOT affected by call forwarding it comes through to your phone even if you are forwarding voice calls.

How did it go in Lithuania?

I'm using the Android 15 beta on a Pixel 8 Pro. Backup calling initially worked with the beta, but 1 or 2 beta updates ago backup calling stopped working. I got the dreaded "emergency calls only" on the non-data line.

The trip to Latvia has been postponed. My boy international trips have been personal. The work phone me remained off.