The real issue here appears to be your Apple iD has been compromised. After that you can manage your trusted device list and start resolving the lost phone problems.
Click on this link "If you think your Apple ID has been compromised" --> https://support.apple.com/HT204145
'Checklist: If you want to see if anyone else has access to your device or accounts' click here --> https://support.apple.com/HT212021
Security and your Apple ID - https://support.apple.com/HT201303
Contact Apple for help with Apple ID account security - https://support.apple.com/HT204169 "This article provides country-specific Apple Support contact information for customers seeking help with their Apple ID password or other security-related issues." Better for directly reporting an issue.
Read the document
'Two-factor authentication for Apple ID' --> https://support.apple.com/HT204915
- "You can manage your trusted phone numbers, trusted devices, and other account information from your Apple ID account page." --> https://appleid.apple.com/
Click on this link for general information about what to do "If your iPhone, iPad, or iPod touch is lost or stolen" --> https://support.apple.com/HT201472
For information about 'How to use account recovery when you can’t reset your Apple ID password', click here --> https://support.apple.com/HT204921