Visible has three ways to contact support: chat, Twitter, and Facebook.
I have had the best luck with Twitter:
If I helped you, please hit the thumbs up/kudos button above.
Wi-Fi calling not working properly is one of the documented issues with the Pixel 6. I've had the best luck with it by selecting the Roaming Preference = "Wi-Fi" under the wifi calling settings. That will default to Wi-Fi calling when the mobile network is not available. To test it, turn on airplane mode (which will turn off your cell phone connection and Wi-Fi). Then turn on just your Wi-Fi and try to make a call. It should connect if Wi-Fi calling is working. You can then turn off Airplane mode so you can get calls when you don't have Wi-Fi. Hopefully, Google fixes this to work properly in a future update.