Xfinity associate lost phone now not eligible for promotion!

On Sept. 26th my boyfriend and I went to my nearest store and did the trade in for my iPhone 15 to the iPhone 17 estimated for over $820. I do not remember specific dates after this, but I do remember roughly the time and days these events happened. My phone was shipped to me and I received it 9/30/25 I work overnight so I could not activate it right away. I waited until the next day I'm pretty sure between 10-11:30am, the associate at the store named Troy helped me activate it. I did not turn in my phone right away because I needed to make sure everything transferred correctly so again I waited until I BELIEVE the weekend of 10/09-10/10 between the same hours and I HANDED me phone the same associate at the store (Troy) the store was very busy so he didn't take any information from me just took the phone from me and I left. When it came time to turn in the boyfriend's phone, I brought it to the same store and at that time a different associate let me know the proper way of shipping the phone back. So, I did ship his phone but made me realize there was no movement on my phone. Which made me contact Xfinity by phone to see if they have received my phone and they haven't, I went store to see if they still had it there and of course they don't. I have opened 2 tickets, and they both have been closed with no resolution. I have also been to the store MANY times and the store manager said she would look at film to see if I actually brought it in its a "whose lying" situation. I no longer feel comfortable going back to that store since they all seem to not want to help find a resolution. I'm currently at the point where i have no idea what to do next. But I do know for certain that I gave the associate at the store my phone, it's now "Lost" and I am now receiving consequences and over payment on my bill for 3 months now. I'm paying $167 when I should be paying not even $120!!!! PLEASE HELP!!