How do u stop sharing with any device with my iCloud?

I believe my device Apple 13Pro Max is hacked or they have control of what I see on my Apple, or might have even gain physical access to this device and setup themselves as a companion! How can I tell or how to stop it? I think “whoever it is” is gaining access through a Mac computer or iPhone 12promax!? I have of course factory rest and I have even changed to 3 new different devices and have even changed my mobile number 3 times as well over the passed 4 months!!!!

please please PLEASE HELP!

Joe

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