I can read a calendar and realize this thread is old news and the OP's situation is long-since over one way or the other, but:
Some North America Dollar/Thrifty locations, meaning I had multiple occurrence's with them and few or none with other vendors, really have charged me for the full cost of the rental plus a further reserve deposit on the front end. This was not every location, was a charge put all the way through and not just a credit line hold, and was promptly refunded upon return of the car.
I had credit line to spare and the price was good enough to not care about it. Finally had enough other issues I left them for good, even if I pay more.