I had just made a 5 day car reservation and then found out the trip would be delayed by 2 weeks. I did not request a cancellation or refund, just to change dates and my willingness to pay extra if necessary. They flatly refuse. SIXT says they cannot make changes without a request from Hotwire. 4 hours with Hotwire and a good hour with SIXT.....Bottom line is I lose the money for the rental and still have to make other arrangements. User's recommendation: Just don't do it.