Unauthorized access to my iCloud account

If you think your Apple Account has been compromised - Apple Support

Note that if you are getting text messages, pop-ups, etc. telling you that your "iCloud has been hacked!!" or things to that effect, these are almost certainly scams, presented by criminals.

The idea may be to scare you so badly that you will contact the criminals for "help", or enter your ID and password into a form on a scam site, so that the criminals can gain access to your Apple account. Access that they didn't have when they sent you the lie that your iCloud was "hacked!!"

If you have fallen for such a scam, you would want to secure the compromised account immediately.