Tax Exempt Refund Problems

Two of the orders I placed with Dell in the past month are supposed to be tax exempt orders. I emailed tax_department@dell.com with the proper tax form and a letter from the state comptroller validating the organization's tax exempt status. This is the same paperwork I use at every other store when I buy something for the organization, and I've never had a problem. I got a reply to the email saying to fax in another form and all the previous forms together. I did that 2 weeks ago, and still have not gotten any response. I sent a follow up email a week ago, and no reply to that, either. Is there a phone number for this department, or some way I can reach a manager of this department? I just want my tax refund to be processed, or at least some sort of update saying they're working on it. It's extremely unprofessional for the staff in that department to not reply at all.