Lied to about promo code

I am reaching out regarding a promotional issue with 2 new Samsung device purchases made on May 19 through my Xfinity Mobile account. When we purchased our 2 phones, the promotion stated it was valid with 'any plan' purchase. Eric, the in-store agent at the North Huntingdon, PA store, confirmed this and assured me and my wife that the two $500 credits would apply, but they "disappeared from the cart" when he went to checkout. My account is currently not receiving the $1000 in credits (reducing my monthly device payment) because the automated billing system is enforcing a Mobile Plus tier requirement that was not part of the initial offer parameters I agreed to when working with Eric. Eric said he'd open a support ticket for us, but we have received zero follow-up and there are no open tickets listed under my account. I tried to chat mutliple times over the past month and a half but no one helped me either. On July 2, I went back to my local store and spoke to the new manager Mikey. Mikey said he'd talk to his district manager and call me back directly from his personal number the next day regarding the missing promotion credits but I did not receive a call from him. Since a company representative (Eric) authorized this purchase under these specific terms, I need this issue escalated to corporate resolutions to have the two $500 ($1000 total) promotional credits manually forced onto my monthly billing statement. We are tired of the run around and need a resolution.