I received a message that my iPhone was hacked

Just delete the message and go on with your day. If you saw the message while browsing the web, then just go to another site. On the internet, a site can either provide a pop-up advertisement or redirect you to another site that shows the ad. You will not want to click any link/button in these messages.

Just continue to ignore similar scam messages that will appear on your phone.

Apple will never send a message like this....even if it might appear that the message is from Apple......so you know that anything that claims to have detected hacking, viruses, etc on your phone are scams trying to trick you into buying useless software.