Xfinity Mobile Sales Rep Lied about buyout promotion

On December 6th, while driving, I received a call from Xfinity Mobile sales rep. He told me Xfinity had a new promotion available that will buyout my current phone balance. I had $277.70 remaining on each line. He said I'd receive a full refund via visa gift card. That's $555.40 total refund expected. He was very convincing over the phone. The new plan was going to save me $50 a month. I figured it was time to switch from Verizon after 12 years of service and save some money. 

The service was switched with many difficulties on both sides. I went to the website to submit my receipts for reimbursement and noticed the promotion only specified a $200 per line reimbursement. before submitting the receipts I called Xfinity Customer support and they told me i was out of luck because the promotion was only for $200 per line not a full refund as told by sales rep. Xfinity sales rep will tell you anything possible to get the sale. No actions for false advertising. This is a poor practice done by the sales team. Now I'm out $155 for switching to a new phone carrier. I'm still waiting for $400 reimbursement, fingers crossed it actually arrives. 

Why do you not honor the promotions that are explained by sales reps.