Beach Body - Product Partners, LLC Unauthorized charge to credit card Beverly Hills California

I am having the same problem with this company. I wanted to order their Rockin' Body program and went through all of the pages...the MANY upsells they had...and when I got to what I believe was the final page, the website said "500 Servlet Error" and that my order could not be completed. Ok, no problem..so I wouldn't be getting this product at this time.
Early the next morning I checked my email, finding not one, but TWO emails from this company stating that my order had been processed. I checked my credit card, which is pre-paid, and sure enough there was Beach Body. Problem is, I was charged TWICE when I should not have been charged at all because their website had an error and informed me that my order could not be completed.
I called customer service and spoke to Gavin, whom I could barely understand and he informed me that I could not cancel this order because "it had already been sent to UPS". Now, my husband and I run a business from home as well as my mother, and we deal with UPS all the time. I know for a fact that they can have that shipment stopped. After 30 minutes on the phone with Gavin, I was frustrated, hung up, called back and asked for a supervisor. This new woman, whose name I did not catch because I did not understand her either, took all my information AGAIN and told me she could help me. I explained to her that no, she cannot help me and that I wanted to speak to a supervisor immediately. After dealing with her for another 15 minutes I was put on hold for 20 and FINALLY got a supervisor. Again, I do not know her name because I cannot understand broken English and heavy accents. This supervisor and I were on the phone for at least 45 minutes, and nothing was accomplished. She basically told me there was nothing she could do because this order had already been shipped to UPS.
I do not know what to do about this. I do not want this product, and my card was charged twice. Because it is a pre-paid card, I cannot have the charges cancelled. I have to "wait until the order arrives and send it back, less the shipping and handling charges".
I am very unhappy with these people. Their website goofed up and told me my order was not completed, yet I was charged anyway. Any suggestions?

Holly
Keyesport, Illinois
U.S.A.