I suggest you talk to the organisation you plan to hire from (most are multinationals so you can talk to them here). Credit Cards are simply the norm for this type of purchase (in the US), where the sum paid is not confirmed until you finally bring the car back. What the rental company wants is to be assured they will get their money, including any excesses from insurance damage, so they take a hold on the money using a CC, without actually putting the transaction through until the car is returned. With a debit card, you complete the transaction at the time of purchase, so its a bit more complicated.