Cannot place calls on any online platforms or even make cellular calls on my iphone xs max.

I am using iPhone xs max. Everything was fine until yesterday evening when my WhatsApp calls started getting disconnected after 1 or 2 seconds. I was on ios 14.7. So I looked on the internet about this issue and one of the solutions was to update my device. I updated to ios 14.8 and then to 15.1. But still, the problem persists. I have tried other platforms like Facebook messenger, telegram and Instagram, but the result is the same. I have tried resetting my network settings, changing wifi networks, restarting my wifi and also using my cellular network. I have allowed notifications on all these platforms as well. I have restarted my phone several times. However, the result is the same. I cannot even make a cellular call.

Telegram call works on my second android phone. So this issue is related to my phone and not my wifi. I would highly appreciate any suggestion except hard resetting and erasing everything.