Dell - Dell Financial Services Continued taking automatic monthly payments out of checking account after product was paid for, Internet

I purchased a laptop from HP through Dell services, my third such purchase from the company. I set up an automatic monthly payment through my checking account.My account was paid in full in 2009 but Dell Financial continued to take the payment out of my checking for two months. I didn't notice until I received an overdraft notice two weeks ago. Realizing the issue was this Dell payment being taken out I tried contacting Dell to resolve the issue. Multiple phone calls & frustration later I finally reached a manager who gave me a fax number to send copies of my bank statement to and to address my issue. A week later and no answer to my fax I contacated them again. After another ridiculous round of phone calls I finally was put in touch with a supervisor named Michelle who said because I had not gone in to my Dell Financial Services account and put an end date on my automatic payments - that was why they were continuing to be taken out. I asked why someone had not notified me of this when they saw the account was at zero and payments were still being withdrawn, and was told they did not notify customers of this. I also asked if I had not gone in and changed that status on my account, which I wasn't even aware of, would they just go on taking payments out, and she said yes. I find this practice to be very shady on their part. I will never do business with them again and I will make sure none of my family, friends or colleagues will either.