Executive Escalation or Legal Dept regarding possible Breach of Contract

I need to direct my escalation to the Executive Resolution team or I will have to take this matter legal.  I responded to an offer to upgrade my service to add DirecTV.  I was offered $300.00 to upgrade; once I found out how much my bill would increase, I refused to upgrade my service.  The sale rep offered me $600.00 to upgrade and I agreed.  I paid the initial amount requested and installation was scheduled.  My service was install and my bill increased, however you have only sent $300.00.  I have been calling your Rewards Center and Customer Service for an update on the balance.  I was told I am not eligible for $600.00 and the other $300.00 will not be processed.  I informed the supervisors and managers I spoke with that my deal to upgrade was contingent on the $600.00 and without it I would not have upgraded.  I ask them to pull the call and confirm the offer and acceptance of the offer and make good on the additional $300.00.  I was told I am not eligible and no one is able to give me the additional $300.00.  I asked for the legal department, as this is a breach of contract and I only agreed to change my service with the inclusion of the $600.00 incentive; without it we had no deal; actually at $300.00 we had no deal.  I need you to make good on my full incentive of $600.00, not even a dollar less or I need to have the information for my attorney to have you served for possible breach of contract. I was told you do not have an escalation process or legal department by Manager [edited for privacy – please do not post personal information]