I am afraid I only answer the questions, you would have to contact customer service about the billing questions. Here is a link to the customer service page with contact us button on the right, and phone number at the top.
You problem is very strange. I have some suggestion that may help with this problem. The first thing I would try is to delete the temporary internet files. To do this, click on start -> control panel -> network and internet -> internet options
On the general tab under browsing history, push the delete button. At a minimum I would delete temporary internet files and cookies, all the form data and saved passwords if you are up for that.
Another thing you can do in the internet options is to click on the security tab -> trusted sites, then sites and add amazon.com as a trusted site.
If those don't help, you could try resetting internet explorer to default settings, this is located on the advanced tab.
If you are not already running IE9, you could try and update to IE9, if you have IE9 already, you could try removing it and go back to IE8 assuming that won't cause problems with your business software.
Another thing I would suggest is to unplug your router for about 30 seconds, then plug it back in. Though it looks like you already tried that.
The only other thing could be a malware infection causing browser re-direction. It might be a good idea to download and install this free program malwarebytes, then update and scan your computer. If they offer a trial, I would decline it. This is not an antivirus protection, only an on demand scanner that works well for removing infections.