block notification

Suggest following either of the two previous suggestion before moving forwards

To assist on future issues similar to this one.

Suggest reading this very well prepared User prepared tip from a well respected Contributor

Phony "tech support" / "ransomware" popup… - Apple Community

This is a scam. Whatever you do, don't click a link or call a number on that notification.

Most likely, these come from Safari notifications that you uniwittingly allowed.

Go to Safari->Settings->Websites, click on Notifications, and make sure to Deny anything that you do not want to show you notifications.

Check Safari > Preferences > Websites > Notifications and delete anything suspicious.

Sounds familiar. 😎