If you receive an email stating that your FileFactory account details have been changed, it's possible that the email address which you used to sign up with has been compromised, and someone has been able to access your account and change your password.
This can occur with very old accounts / email addresses, when it was more common for people to use the same password across multiple accounts.
The best way to resolve this is to contact FileFactory Support.
You can check if your email address has been hacked by visiting this service: https://haveibeenpwned.com/