Someone is using my account without permission

Change your password: Change your Apple ID password - Apple Support

Also see: If you think your Apple ID has been compromised - Apple Support

By changing your Apple ID password, changing your security questions, and securing your trusted recovery devices and trusted email accounts, most commonly. By changing those items which grant access into your Apple ID. You’ll also want to look at any other local access into your computers and devices, as access to those too can expose your passwords. You’ll want to enable two-factor authentication, if that’s not already enabled.