Issue with Xfinity reward $830 off iphone

Hi, I received multiple emails about having a reward to get $830 off while buying new iPhone pro. It was clearly mentioned no trade in was required to avail it. Only a promo code would be needed. I tried to order it online but it said back order or something. So I called customer service and provided the promo code. The CS lady processed the order. I received the phone and activated it but I did not receive the 830 discount in two consecutive bills. I called customer service multiple times and they created ticket after ticket but so far no communication on those tickets. I am feeling like being tricked to buy a new phone and switching services. This is really frustrating. I am loosing patience and trust in Xfinity.