Hey JMN7542,
Thank you for using the Apple Support Communities! Congratulations on your new iPhone 13! We understand you're unable to use iMessages so let's get you the help needed to get things working.
Based on your description, it sounds like your phone number isn't activating with iMessage. Navigate to Settings > Messages, and see if there is an alert that relates to activation failure. If you do see one there, please follow each step in this article: If you can’t turn on or sign in to iMessage or FaceTime
Keep us posted if you need more help with this issue after that.
Best regards.