Walmart.com Charging for a returned pool

Order number 2000112-36986261

I purchased a pool from Walmart.com and paid via affirm.com. It came in 3 boxes via fedex. Fedex only delivered box 1 and 2 and said that box 3 was lost in transit. I started a return on the pool since I only had a partial pool. I forgot to print the return label and fedex picked the boxes up anyway. A week later, fedex delivered box 3. I returned it with the return label and got a partial refund for the  box 3. I assumed fedex would call me about the boxes and after going back and forth with them for two months, they said it was returned  to Walmart. Walmart customer care said last week they would do a manual credit for $404. I reached out to affirm and they said there’s no returns. On the chat with Walmart.com now and they’re saying I still need to contact fedex. Affirm won’t give my money back and is ruining my credit due to none payment. Fedex who started all of this confusion won’t allow me to do a claim because Walmart cancelled the tracking number. Walmart won’t refund me and is trying to make me pay for a pool I don’t have. I’m going to contact the new station and get a lawyer if this is not resolved soon