Terrible service from DFS (Dell Financial Services)

I have had ongoing problems with Dell Financial Services since April 10, 2015. This was in regard to two lost payments that were verified by my bank to DFS with proof of payment documents. Every call I made was greeted with apologies and the promise to solve the error and phone me in 24-48 hours. I made at least 10 calls, even getting my bank involved in a three way calls. Every time the Dell service pleaded ignorance not about the issue even when presented with a case number. During this 6 week period I was never contacted by Dell. Finally I received one credit after four weeks but the last has never been credited. The last 3-way call was on Tuesday May 19, 2015. The Dell rep, Sally, assured me that she would contact me with information on this issue within 24-48 hours again. I asked her to assure me again that I would get a report from her within this time period (witnessed by my bank representative). She repeated her assurance. It is now Friday, May 22, 2015, 72 hours later, and I have not been contacted by "Sally". This was a repeat of several calls made over the past weeks. It's very obvious that the customer is not a priority for Dell and Dell Financial Services. I have purchased Dell products for many years and own four Dell computers at this time. They will be my last Dell products. Unacceptable customer service.