Apple Watch Series 3 GPS+Cellular iMessages on watch not syncing to iPhone and vice versa

Hello,

I'm having an issue where iMessages initiated and replied to from my Apple Watch don't appear in my iPhone and vice versa; any iMessages sent from my iPhone don’t show up in the text message thread on my Apple Watch. It’s frustrating A) not knowing if a message was sent or not and B) simply not having the text thread to refer to because messages from the watch don't sync.

I've unpaired and re-paired the watch 3 times. I've turned off iMessage and turned it back on. I've checked that Mirror iPhone is the marked option in the Apple Watch app. I've signed out of Apple ID and signed back in.

What's weird is the phone calls made from my watch sync to my phone, as well as emails I've sent from the watch show up on my phone..but not the messages.

Anybody else having this issue? I spent 3 hours at the Apple Store and received a new watch. In the end they told me that it must be an AT&T problem.

I really think it may have something to do with iMessage being driven off of the Apple ID phone number that is connected to the account. The send/receive messages from this number listed is my cell phone number when the watch has its own dummy number assigned by AT&T.