I am becoming a huge fan of Sixt after renting with them the last time I traveled home to Miami. Once again I booked with Sixt (prepaid) 83 days in advance and subsequently signed up with the mobile app. A day after booking, I realized I had the days wrong and wanted to modify the booking to shift the days up one so it coincides with my arrival. Sixt wants a rebooking fee. Not a good look from Sixt for a reservation that is so far in advance. Additionally, attempts to load last year's reservation has proven unsuccessful as the mobile app is asking for a security code that last year's booking (**********) did not have. I was hoping that coupled with my current booking (**********) that it would change my member status. Even so last year's booking was not made that far in advance and I got a better price point than I did for an advanced booking. So with no price protection I am regretting prepaying rather than simply reserving. How can I modify a prepaid booking without incurring fees and how can i get credit for past rentals with Sixt? Thank you in advance.