What is Wi-Fi Calling?

Wi-Fi Calling routes normal phone calls and texts over a Wi-Fi network instead of the mobile network — a lifesaver in buildings with poor signal. Calls use your normal number and usually cost the same.

Find it under Settings → Network & internet → SIMs → Wi-Fi Calling (or in the Phone app's settings). Both your carrier and your plan must support it, and most major US, UK and Canadian carriers do.