Trade In Issue

Long story long, I bought an iPhone, with an added trade in of my iPhone 8.

I had to cancel that order because I accidentally ordered the wrong one. So I order the correct iPhone, along with a trade in of my iPhone 8.

The trade in kit came, and I sent my iPhone 8 in the kit, with a printed page of my trade in order. I looked up the fedex status and it has been delivered.

A few days later a second trade in kit came. The status of my trade in, is now waiting for me to send in the iPhone 8. But I already have, and haven’t received a refund.

Sorry for the long story, what should I do?