Let's see if we can get this figured out. Do you happen to have a different device to test your SIM in to see if WiFi calling will work on that device without error? Our tech teams have a couple more steps they're able to try in one of our systems and if that doesn't work, the last step would be to file a ticket with our engineers.
Happy Friday, makenna!
Just swinging by to see if you've had a chance to look at my previous post. If you're still having issues, please get back to me with answers to the questions I asked. If your WiFi Calling is good to go now, let me know!