Apple Watch supports roaming from the watchOS 9.1 software version (starting with the Watch series 5), and the phone must have at least iOS 16.0. Roaming on the Apple Watch only works over VoLTE roaming networks. You can check the availability of VoLTE roaming on the Telia website. If the selected country and operator show the ‘Network type’ as: 2G, 3G, 4G, 5G, VoLTE, then VoLTE roaming is available on this network. To use roaming, make sure that roaming is enabled in your watch settings.
With Samsung watches, you can use the call service, text messages and data services abroad. At that, you should take into account that in the case of calls, some countries display the main number when calling out, while some countries display the additional number when calling out, depending on the network interface technology. For messages, the main number is displayed when sending an SMS, and the additional number when sending an MMS.