Issue: When calling on any VOIP Service (Whatsapp, FB Messenger, Snapchat, Telegram etc), the phone does not have any access to Internet in the background while connected to WiFi

Explanation:  

Like the title says, the call quality is absolutely normal, no delay no stuttering etc. But when I remain on call and browse the web, I get NO CONNECTION.

I can't even open the router gateway portal aswell

All while my call is running fine but with little lags

Phone: Poco X3 Pro, Realme narzo 20 pro, iphone x , all facing same issue

Internet: Local Internet, provided through PPPOE login in Wireless WiFi Router.

I believe there is a problem with the settings of the router, if anyone can help me with this I shall be immensely grateful. We can also discuss this issue on Email and then update the community regarding the solution

I have tried many solution from Google , YouTube etc, but none of them worked.

Thanks in advance!