Setup Cellular Data on iPhone 15 pro max with xfinity, is not working esim wiill not work

For 3 days customer service at xfinity store and online reps have been trying to get my new iPhone 15 pro max to work and all I keep getting is eSim cannont be added. : this code is no longer valid. Contact your carrier for more information. The QR code has been sent about 12 or more times with the same error message and no one able to fix it !! help please no phone now for 3 days.