No toggle for WiFi Calling on Apple Watch

I was able to contact my son and ask him about his settings. Understand, this is related to AT&T, our carrier, so others may differ slightly. When going to Settings>Phone>Wi-Fi Calling, he turned it on. After doing so, and it activating, an additional switch appeared beneath that that says Add Wi-Fi Calling for Other Devices. Once that was done, and the phone was restarted, checking the Watch app on the iPhone, a toggle for Wi-Fi Calling appeared. That switch did not appear on the iPhone until after Wi-Fi calling was activated on the iPhone and the iPhone was restarted.

That is the best information that I can provide for you. Hope that helps.

Does you carrier support wifi calling? If not it will not work.

Is wifi calling enabled on your phone? If not it will not work even if your carrier supports it.

Make a call with Wi-Fi Calling

Please forgive a very basic question. Do you have the cellular version of the Watch?

Call Apple Support.

I do not recall seeing a switch on the Watch app on the Phone, just a way to turn on wi-fi calling on the phone if your carrier supports it, and then add the watch to your devices on the phone. See if this support document helps. Make a call with Wi-Fi Calling - Apple Support

Well, I don't see that switch on my Watch app, but then again, I don't have wi-fi calling turned on for my iPhone. My carrier does support it, but I just choose not to use it. Something there might make a difference. I also have a Series 4 watch that is GPS + Cellular, so I don't know if that makes a difference. I do know from my son, who has a Series 3 watch, GPS only, that he has made wi-fi calls with the watch, and he has wi-fi calls turned on for his phone. I'll have to contact him to see if that setting appears on his Watch app on the iPhone.