iPhone xs SMS message fail to send. "Number not Available"

magenta10342943

    I activated my new iPhone 11 yesterday and ported the number fro ATT (over 24 hours ago).  I am unable to send SMS text messages.  When I send one, I receive the message "number not available. which number would you like to send the message with". The options I get say "Primary" or "Cancel".  If I select "primary" and send the text, the text fails to send (though there is one recipient who did receive it but 3 others who do not).  I am able to make calls and send iMessages with the phone.  Please help! 

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