No dial tone after mandatory phone upgrade

I'm not a Cox manager.  The tech in your home was waiting for the Help Desk to provision your telephone modem (eMTA).  To provision means to verify your eMTA and then initially configure the eMTA, network, Cox equipment and your account.  It's the initial setup.  If your service isn't provisioned; rebooting, resetting and troubleshooting would have no effect.

"Upgrading" your service requires more than just replacing the modem.  The tech also has to rewire your patch-panel from circuit-switching to packet-switching, test for ingress, administer a third-party verification and close the ticket.

The next time you call, tell them to provision your phone.  If the rep can't provision, the rep will provide the obstacle.