I received a message my cell and messenger is being used by a new Apple device

Have you signed in on another device recently?

What kind of message?

Several possibilities. One is this is a real message. The other is this is phishing.

Scams (e-mail, text messages, and phone calls) are getting very good at closely imitating true Apple communications. Always be cautious. Here are some guidelines:

Identifying legitimate emails from the iTunes Store - http://support.apple.com/HT201679

Recognize and avoid phishing messages, phony support calls, and other scams - https://support.apple.com/HT204759

If you are uncertain about a message and a resource provided in that message, do not click on any links. Try to independently verify the resource by going to a support page on apple.com and use that to contact Apple or to verify the service the message is telling you to use. Read the article below about ways to check if somebody really has logged into your account.

Click on this link "If you think your Apple ID has been compromised" --> https://support.apple.com/HT204145

'Checklist: If you want to see if anyone else has access to your device or accounts' click here --> https://support.apple.com/HT212021

Security and your Apple ID - https://support.apple.com/HT201303

Contact Apple for help with Apple ID account security - https://support.apple.com/HT204169 "This article provides country-specific Apple Support contact information for customers seeking help with their Apple ID password or other security-related issues." Better for directly reporting an issue.

I received A message saying your Apple ID and phone number are now being used for message and FaceTime on a new Mac. What does this mean

Did you read what Limnos posted and read the links they posted? It could be a scam or someone may be using your Apple ID.