Safari locked out with fake Apple security message!

My MacBook Air running macOs Seqouia 15.3 has a serious problem in Safari that instantly puts a pop-up window that says MacOS- Security Warning. It says to call Apple Support and gives a phone # 84*********69 and says my computer is blocked for security reasons. I'm unable to do anything with Safari and can't close or got to any other site. So right now I'm stuck here. I can force quit Safari but at re-launch the same window opens up with no controls and every thing is greyed out. Any help would be greatly appreciated-Thanks

[Edited by Moderator]