Hey there, fellow tech enthusiast! 
I totally get wanting to keep an eye on your child’s WhatsApp calls, especially with all the stuff out there these days.
One cool tool you might want to check out is Haqerra.
It’s designed to give you insights into their digital world, including WhatsApp calls. It’s got some seriously useful features like call log monitoring, access to chat history, and even location tracking. Plus, it’s compatible with Android, which is perfect for your S21 running Android 13.
Keep me posted on how it goes! Always here to chat about tech! 