Unknown text message on lock screen

It is spam! Someone is phishing for your identity. Ignore it, and/or report it to the authorities.

^^ ignore it

Why would you send this to me?

I already said "ignore it."

Go to messages. On that message, at the top right, tap "details". Tap the "i" in a circle at top right on the next screen. If there is a phone number, scroll to bottom, and tap "Block this caller". The spammer may use another number, but this should work for a while, anyway.

It's what's called a "flash message". It's using a system that's primarily used by carriers to send account information to the phone. However, on some systems, it's possible for users to get into the system and send messages. People often do it as a prank.

This article gives a suggestion on how to block them:

https://snapguide.com/guides/deactivate-flash-messages-in-iphone/

As I don't have this option on my phone, I have no way of testing it.

Glad it helped!

Those can be a little bit unnerving it you don't know what they are.

You are lucky that your phone had a passcode and you can unlock it. However, my wife did not have a passcode and someone switch her phone in Lost Mode and set a new passcode, that is why they ask you to contact them to get unlocking passcode.

The bottom line is I do not know right now how I can unlock my wife's phone without erasing all information on it. :(

Well, I maybe wrong, but I have exactly the same message and the phone is actually locked through the Lost Mode. Maybe they did it by hacking the iCloud\AppleID or something similar, but that does not really matter for me right now. Also, if you just do a search for that email address you will see many people with similar problem - not just a flash message, but the locked devices as well.

BTW, in my case I can delete that message on the sceen by removing it from the Lost Mode setup (but I couldn't turn the Lost Mode off without a valid passcode).