WhatApp does the same for UAE numbers. If I initiate a call to my sister who lives in UAE I get an error saying that "Whatsapp calling is unavailable in the UAE" or something along those lines.

We worked around it by installing Signal, but she needs a VPN to be able to access it since it's completely blocked in the UAE (as well as Oman).

We get around this by texting each other before hand on whatsapp with the keyword "vpn" and then talk to each other over Signal. Quite the hassle.