IOS 16 call waiting

Hi,

I'm having a problem with call waiting since upgrading to iOS 16 on my iPhone 13 UK.

It is disabled as that's how I like it (to not receive a call while in a call) but no matter if it's disabled I still receive a notification in form of beeps of an incoming call while I'm on a call? This is for ordinary calls not WhatsApp etc. Am I missing something as in iOS 15 my callers would be met with a busy tone while I was already in a call?

Thanks,

Richie