I am facing the similar issue after upgrading to IOS 14.3 this week & tried calling Apple Support as well as Jio Care but it seems Jio support executive does not know the W of WiFi Calling Support and moreover they asked me to send an email to log a case saying they can’t log a case through call.
Apple Care wants to have a ticket number from network provider and network provider say this is iPhone feature and they can’t do much 🤪 I think I will have to port back to Airtel 🤓 pathetic support from Jio.
I tried resetting the network settings, Apple support executive was not sure if that would result in loss of eSIM settings or Data Plan, and I happily offered myself as their guinea pig 🤪 and fortunately it didn’t result in loss of data plan. I also tried soft reset of iPhone as well but no luck.
conclusion - the customers are left at their own fate due to software bug caused by this update, lesson for me - not to enable auto update of iPhone and wait for stable release.