NFC notification on my iPhone

Ssteppe wrote:

says my phone has completely overtaken by somebody else

You have been scammed, and almost certainly provided all your credentials to the thief by responding.

Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support

If you think your Apple ID has been compromised - Apple Support

It probably said "NFC" – an abbreviation for "Near Field Communication", which I believe is a technology that lets you hold an iPhone or Android phone up to a gas pump or other terminal to pay for things.

That's trivia. The more important thing is that the notification was almost certainly part of a "phishing" scam. A notification that appears out of the blue, with references to "NFC" and "CashApp" and such, practically screams FRAUD in flashing neon letters.

In addition to reading the article on what to do if your Apple ID may have been compromised, read the section on "What To Do If You Responded to a Phishing Email" in

Federal Trade Commission – How to Recognize and Avoid Phishing Scams

Ssteppe wrote:

I’ve never given it to anybody but the person who’s doing it is inside my house and he won’t leave, so is there any other suggestions I can do it for us to stop this I mean I’ve been to the police they said he’s not doing anything so I have to get his girlfriend because she’s one doing it.

This is a problem outside the scope of what we (other users) can help you with, or what Apple Support could help you with.

If you have an untrustworthy roommate ("the person who's doing it is inside my house") who "won't leave", then I can only suggest that you never enter your passcode or other credentials while this person is watching you do it; and that if you write them down, that you do not store the piece of paper some place where this person would be likely to find it.

What you can do is carefully read all the information provided above, and take the steps recommended according to your particular situation.