Call forwarding spinning wheel

I am not able to receive or make any voice calls from my iPhone 12.

My 3G works fine over the mobile network.

Upon some research and trying various methods like restarting phone and checking donot disturb and playing with settings I came across a thread here to check the spinning of call forwarding.

Im facing the same, attaching a screenshot, following the steps there to turn off mobile data and then restarting the phone also isn’t working for me.

Please guide me ASAP on how to fix this.