Problem with Dell Financial Services that needs Dell's attention

I know that I should be able to resolve my problem with DFS by contacting them, but that has been unsuccessful. After dealing with them for over six weeks and not receiving a refund of an overpayment of $177, I wish to make a formal complaint to Dell regarding their financial services contractor. I have complied with every request, including involving my bank to verify a payment that they claim they cannot locate. This is the second $177 payment that was lost in their system. The first was finally located and refunded two weeks ago. I receive the same lip service every time I call and an assurance that they are looking into it, expediting it, and will contact me without 24-28 hours, etc., which they never do. I call every few days and they act like they have no idea what I'm talking about and I have to start over. Several case files have been created. Can anyone tell me how to reach someone who in truly interested in customer service at Dell (not DFS)? I have been purchasing Dell products for years and hate to leave the fold, but this experience has me headed in that direction.