Apple Card only giving Partial Refund

I am hoping to get some advice because I have been going back and forth between Apple Support and Goldman Sachs without any resolution. I ordered a MacBook in July and the order showed it was shipping to the store, but it was never ready for pickup. After waiting about three months, Apple automatically canceled the order. Recently I noticed that a refund was issued, but I only received part of it. I had made three monthly installment payments, yet the refund only covered two payments along with the tax.

I have already provided proof to both Apple and Goldman Sachs that three payments were made, but Apple tells me to contact Goldman Sachs and Goldman Sachs sends me back to Apple. I am stuck in the middle and do not know how to proceed. Has anyone here faced a similar issue or can suggest the best way to get this resolved?