invoice error

I have spent two hours on the maze of phone options; when you are asked for your order number and you give it, it connects to another automated person telling me thank you; goodbye. I recently purchased two laptops which were on sale but just noticed that I was invoiced the full amount, not the sales price. I am simply trying to speak with someone about that. Customer service seems to be non-existent and will make me reconsider my purchases from dell for my business in the future. In addition, I was planning on buying two more laptops and requested a sales call back (twice) with no call!