AT&T employee made sign-up offers, outlined in an email, then disappeared. Now I am left in limbo...

Hello, due to a number of issues I experienced when initially setting up my service I had decided to go with Spectrum in lieu of AT&T. I was then transferred over to a specialist who made several offers to get me to sign up with AT&T instead of Spectrum, including two free months of service (phone and internet). I have this in writing sent from the agent in an email to me. He instructed me to email him after receiving my first and second months bills so he could take care of them for me per his promise. Now however he is not responding to my emails and no one that I've called at AT&T can see a record of this conversation, any notes, and as a result is unwilling to help. As a brand new customer I am only asking for what was promised to me, please help!