How do I report a Security breach?

I am very frustrated here... My apple id all of the sudden didn't let me use my password. I had to change it even though I knew I was using the right password. When I log into Appleid.apple.com and reset my password I noticed that my account was all different. it had different address and name. Like if somebody hacked it and change all my information.

This was the information that replaced all my personal information:

Name: Son Nguyen

I don't know who to ask or how to report it. I wonder if more people has experienced the same thing.

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