Did I send my trade-in device to the right place?

The same thing just happened to me in Feb and they still have not been able to locate the phone I dropped at the post office. The post office is trying to locate it as well but it has been weeks. I have still had to pay the monthly fee for the phone I bought and returned it a week later and got something else so now I am actually paying double because of this. The scariest part it is an expensive phone and it was the fold 3 from Samsung. I have talked to customer service about this a bunch of times and get nothing is there anyone else that can help figure this out seems like others have had the same issues which makes me worry even more. The post office asked if the package had insurance and that made me think that surely Tmobile would add the insurance to a package that is containing an 1800 phone to be returned thru the mail which was the only way for me to return it I asked if I could return it to a store.