Trade in phone credit

i did the trade in promotion back in September 2025. I ordered a IPhone 17 pro max silver and orange. We did the promotion online so we have to ship the trade in phones back to the center and won’t let us drop off in store . We ship both iPhone 15 pro max to in the same transaction with USPS but USPS lost the trade in phone for the orange pro max in transit while the other one received. I been calling the customer service since last year, been calling over 10 calls now. Every time I call, the representative just tells me that they are opening a new ticket and going to follow up with me within a week. Never receive a call nor respond on email back from them. I called 2-3 weeks ago and the representative said the result will be given back to me through phone or email in a week. Never received any response and I just called. The new representative said to wait another 7-14 days. It’s been over half a year. The investigation still not done? I don’t know what to do.