Transfer data from old phone to new phone before or after contacting carrier

I decided to contact my carrier AFTER I transferred my data, and am glad I did. My old iPhone was an 8 Plus so the new eSim method wasn't possible. The carrier required two IEMI numbers for the new iPhone 14 Pro Max. One number was on the box it came in; the other number was in Settings "About". Because I'd already transferred apps and data, it was easily accessible. Also, when I called the carrier, they immediately deactivated my old phone. For only a brief period I had no working phone, quickly resolved because all my data was already on the new iPhone.

Thanks for your input.