set up wifi calling

SMS, MMS, WiFi Call, Call Forwarding, Call Waiting, Call Merge, Conference Call, Hotspot, Voice Mail (Visual or Normal) all are Carrier Specific features. Contact your Carrier (Cellular Service Provider), the agency that issued the SIM / eSIM to you.

Did you try just turning it on as per my reply?

If the carrier agency has allowed it, go to Settings, Phone, Wifi calling, On