Trade-in value never received - no one can help me

I traded in my phone on September 27th, 2019. I have called 5 times, gone into the store twice, and routed from department to department with no one willing or able to help me. In-store, I was told that I would receive a bill credit. When I hadn't received it by December, I called. I was told that I would see it by the next billing cycle. I didn't, so I called back. Told the same again. I didn't, so I called back again and was told that it shouldn't be a bill credit, but rather a reward card and needed to go into the store to have them resolve it. I went into the store, they told me it was being escalated. I returned to the store and was told it was being escalated again. I called back again to the loyalty department, who told me I had to call the trade-in department, who said she couldn't help us, wouldn't escalate it, and wound up hanging up on us when we insisted on speaking with a supervisor. We can't get anyone to take responsibility to resolve this. I need help!!