Apple ID Refuses to Be Removed & iMessage Refuses to Activate

I've encountered some programming bug that I can't find a workaround to. The issue is that I cannot be reached on iMessage at my phone number. I just bought my first iPhone ever and iMessage is linked to my email account but it simply will not activate with my number.

So, iMessage and Facetime work on my phone (over cellular or wifi) but iOS shows my Send & Receive account as my email. When I open that screen my number and email show on the screen with the email having a check mark next to it. I can press the number and it will have a spinning wheel for awhile, but it will not activate. I've tried all the normal fixes and talked to Apple Support (typically useless). I'll detail more of what I've done below but let me explain the potential complication.

I used iMessage on macOS before I had an iPhone. That of course shouldn't be a problem, but it was obviously using my email for iMessage with I was on the Mac. So to try and remove any conflict, I want to remove my Apple ID from the Mac. Well I cannot. I have signed out of iTunes and deauthorized the computer (several times with restarting the system). I have signed out of iTunes (restarted the system) and I have signed out of iMessage (and restarted the system). Nothing anywhere on the system that I can find says I am logged in with my Apple ID. My Apple ID page (appleid.apple.com) shows NO DEVICES linked to my account (I have my iPhone disconnected for now). But guess what, when I turn the iPhone on, it tries to authorize iMessage and I GET A POP-UP ON THE MAC TELLING ME I"VE SIGNED INTO IMESSAGE ON AN IPHONE.

How is the Mac still linked to my account?

Please help my disconnect this Mac from my Apple ID (it's a work computer so it really shouldn't be linked anyway).

I'm not sure that this will fix the iMessage issue on the phone, but it sure couldn't help.

What I've tried to fix iMessage on the iPhone
Turning iMessage and Facetime off and on (with and without restarting)
Signing out of iCloud, turning off iMessage and Facetime and restarting.
Signing out of the Phone everywhere I can find.
Updating my payment info on appleid.apple.com
Talk to Apple support (they asked if I've tried turning iMessage off and on, I spent an hour with them)

This is dumb.