Call History: How to Delete very old calls, especially blocked numbers

I want to delete calls from my call history that are over 90 days old and calls from numbers I have blocked.

How can I do this?

Note: The root cause of my question is that my AT&T phone shows 20 Missed calls. The AT&T forum stated this is a function of my Voice IP provider, which is "Xfinity" I want to delete my call history so I can clear this message which serves no purpose or functionality to me.