在SIXT订车，取消预订后是否收费？

本来打算9月19号出行。车、房、机票均已定好，但是太太8月27日重病住院，计划泡汤了，随即开始取消一系列预订。损失惨重啊。
我给SIXT发了EMAIL取消预订，但是看回信好像要收费啊，租金才700欧，居然要收140欧！求教怎么破！
以下为SIXT的回信：
Dear Mr. Zhang, Thank you for your e-mail. You have choosen our prepaid tariff.In case of cancellation a fee of 139.19 EUR will be charged. You can either change your Booking via www.sixt.com/rebook
or cancel your reservation via www.sixt.com/cancellation . Best regardsMarcus Bartels
以下为我的去信：Dear SIXT: Since my wife's health reasons, we can not travel to Germanyaccording to our plan . So I have to cancel the Booking at SIXT. Bookingreservation number is: 9801234929. Booking vehicle: CLA. Booking date:September 19, 2013 - April 10, 2013. I look forward to rent a car in SIXTwhen traveling to Germany next time. Thank you! ZHANG