I have the same problem and I wrote Amazon a complaint letter, and below is what they have replied:

Thank you for writing to Amazon.com.

I would like to sincerely apologize for this billing error associated with
your order. At Amazon.com, it is our intention that we provide the best
service possible for our customers, and we realize that in these cases, we
have not provided that.

I have requested a refund of the erroneous billing to your credit card.
This refund of $14.54 will be reflected on your next credit card
statement. Although it certainly cannot make up for the inconvenience
this has caused, we would like to give you a $20.00 promotional
certificate, for use toward your next Amazon.com order. When you redeem
your promotional certificate, please be sure to use the shopping cart
rather than ordering via 1-Click.

You will find all of the details below. Simply print this certificate
or save the message on your hard drive for future reference.

Again, please accept our sincere apologies for this inconvenience. We
hope to see you again soon at Amazon.com.


Best regards,

Richard泎eattie
http://www.amazon.com

So I am not only get my refund back, but they also give me a $20.00 promotional certificate for Free to use for my next purchase!

This is what I call 100% CUSTOMER SATISFACTION!! Cheers Amazon!!