Thanks for responding momaj2005,
The link provided at the top of the previous message, provides information on what to expect when changing your Apple ID region, by explaining what steps you need to take before making the change.
We can't say for sure how the change was made. That said, if you suspect or are concerned that your Apple ID has been compromised, the following page outlines the steps you can take to secure your account, and ensure you're the only one with access moving forward: If you think your Apple ID has been compromised
Cheers!