Installment Plan: Return or Trade?

I'm not necessarily looking to do this but I'm just curious...

If I'm midway through my Installment plan for an iPad Pro, is it possible to turn it back in or trade it for something else of equal or lesser value? How does that work? I've barely used it at all and it's in excellent/like-new condition. I'm just wondering if there are options or if I'm locked in via contract until the installments are fully paid.