How to remove Apple ID if you don’t have the phone or know the apple is
How to remove an Apple ID from a apple when you don’t remember Apple ID
iPhone 7, iOS 15
Is this about activation lock?
If you're the original owner of the iPhone and you can prove that, then you can start an activation lock support request by Apple. See this Link on how to do that How to remove Activation Lock - Apple Support
If you're not the original owner, and you own an activation locked device you must ask the original owner to remove the activation lock