Just update your Apple ID with your new phone number. Remove your old phone number and pull the SIM card out. I went from a carrier to another ESim carrier and it was wonky at first. Just completely remove the old number from everything regarding Apple, but make sure you keep your recovery questions and email up to date. Then it’ll fix itself
I usually like “getting the shiny new toy” as mentioned in another comment. But my 12 pro max will be good for another 2 years (4 years of ownership) as the newer models don’t excite me.
People have had their iPhone 7+ and 8+ since they came out and are perfect okay. I think an average of 6-7 years is plenty.