我寫信給AMAZON，剛剛也收到回應了。
信的大意是說，我所提到的折扣都有算進去，也就是Total paid by Credit Card才是他們收取的金額；他說如果有任何額外多收的費用，願意退給我。
以下是郵件原文：
Upon investigating your order, I found that it did qualify for all of
the promotional discounts you mentioned.

Please note that we have charged your credit card for $91.16. However
we will be glad to issue a refund of these additional charges if
there will be any. To ensure that we refund the appropriate amount,
we kindly request you to wait until the entire order has been
shipped.

When you have received our e-mail confirming that your order has
shipped, please write back to us at . If possible,
please include a copy of the cost summary from your original order
confirmation e-mail. We will make sure to request the appropriate
refund to your credit card if there will be any discrepancy.

I hope this solution is satisfactory. Once again, I apologize for
this inconvenience.

Thank you for your patience in this matter, and thanks again for
shopping at Amazon.com.


Best regards,

Pankaj Sharma
http://www.amazon.com
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Check your order and more: http://www.amazon.com/your-account