Welcome to the Community, @JodyM.
When you activated the new phone, could it have tried to move your SIM over to an eSIM?
This is one of the features within the quick start options on a new iPhone, but it wouldn't explain why you would lose service to your Apple Watch.
It's also worth taking a look at our network status checker so we can be sure there's not anything in the area that could be affecting you, too.
Peter
