wifi calling on other devices when iphone NOT nearby will not enable

the solution to this problem was to replace the sim card which was transferred from my old iphone when I upgraded. The ATT tech support guy argued against this saying "the phone is still under warranty, get Apple to replace it". Finally he agreed to replace the sim, and all was well. There was another issue, just as subtle, which was the free ATT call protect feature was not working, even though it was enabled. All fixed.

thanks again for your response. I worked extensively with ATT on this. No solution was determined. Everything on their network appeared normal. I'm hopeful by posting here that someone else has run in to this and found the solution. I'm suspicious of some sort of icloud issue with respect to the iphone itself, one step taken of course was to sign it out and in of icloud, reset network settings, etc, zilch. Just to reclarify, wifi calling on the iphone works great, receiving and making calls using other devices when the iphone is nearby also works fine. What doesn't work is wifi calling on other devices when the iphone is NOT nearby. Thanks for your input.

Thanks for your response. It’s not about WiFi calling itself which works fine, what fails is WiFi calling on other devices. I worked extensively with att on this, not fixed.