Phone stolen

In December of 2024 I brought my old phone in to do a trade in. I am still in March 2026 getting charged for the new phone. I called xfinity to see how much longer because I should have a trade in credit and they said there is no record of a trade in on the account. They told me I have to go to the store. I went to the Southfield Michigan store, where I did the trade in at, and they also said there is no record. They looked who did the trade and the guy who did it, I think his name was Lawrence has a record of stealing peoples phones and that’s why he doesn’t work there anymore and he’s in jail. The assistant manager told me this and said that he probably stole my phone. He said that he was gonna do something about it and I should expect a call in 2-3 days and I have not received a call and he has also not gotten back to me like he said he would. I’ve tried calling again and they can’t do anything on the phone and told me to go to the store and the store is also not doing anything. At the time I traded my phone in it was worth 450 dollars please help that’s a lot of money