My phone is saying it has a virus

SCAM! Your phone can't get a virus unless it has been jailbroken. Do not reply or give them any personal info. Just delete and move on. Check this link...

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

Restart the phone to see if that gets rid of the pop-up. Don't download anything!

As above, it is a scam. It is a scam 100% of the time, no exceptions. Close the offending page and avoid sites that are involved in such bogus advertising tactics. Never download anything based on a popup message.

Phony "tech support" / "ransomware" popup… - Apple Community