Trade-In Stuck "In transit," 4th Bill No Credit in Sight

Okay not sure how this going to sound coming out, but I'm beyond Frustrated with this company. Recently (4months ago), I transitioned from my parent's wireless account to my own account and then after doing this upgraded my phone by paying off the Samsung Galaxy S20 FE 5G that I had on my parent's account and then by submitting for a trade-in to get a Samsung Galaxy S22 Ultra. Upon using the form my S20 was deemed worthy of an $800 trade-in credit. I followed the instructions, received my new phone, and used the provided materials to ship my S20 back to at&t. I received my new phone and the Return materials on October 28, 2022, and shipped the trade-in phone by October 31. I proceeded to receive no tracking updates at all whatsoever and didn't think anything of it at the time. Last month, which was my third bill since sending them the trade-in, I noticed that I still had not received the trade-in credit and so I dug into the status of my trade-in. Shipped via USPS the only update available from the tracking number posted to Pitney Bowes for me to track the package was that on November 14, 2022, it was "handed off to a shipping partner." With no other updates and no one to contact I attempted to follow up with at&t's customer support to determine if they had received my old phone and when my credit would start as their policy is "within 1 to 3 billing cycles." After discussing with the support rep, who was absolutely terrible and had no concern for me getting my credit whatsoever, with the help of my mom I was able to strong-arm the credit out of them or so I thought. I have my bill for the following cycle due by Feb 31, 2023, and the credit has disappeared from my account. With Pitney Bowes still having no further updates I am extremely frustrated confused and asking if anyone has advice on the next steps. Honestly considering a complaint with the better business bureau but I will attempt to call support again on Monday first.

I am a college student and need the credit I was informed I would receive due to financial uncertainty. Hoping this gets seen by the right people. Thanks for any help.