Issues reactivating an iWatch on another carrier.

I have an iWatch 6 that was previously on AT&T. When upgrading to new iPhone 13 Pro, I also ported the number used for the iWatch. After multiple attempts to reactivate including totally resetting the watch and phone, I still have no cell connection on the watch. I purchased the cell model for the fact I don't always have my phone with me when needing to make or answer a call. Anyone have a suggestion to resolve?