Trade In still in process after 3 months

Traded in three phones, one went smooth and two others are still pending after three months.

Reached out to chat and was told they were to be reflected on the next bill, TWICE! Tried again and they are still telling it's in process but can't give an actual status/reason of why I was lead to believe they were ready to go in two previous occasions.

Items show as delivered on USPS tracking , so there's nothing pending on my end. Have no other way to check and starting to get worried as there seems to be many posting in forums mentioning similar issues with trade-ins.