Refund dispute

We made a booking on line on the 18/03/2018, unfortunately on the 19/03/2018 when we got to the airport the terms and conditions I got were unacceptable then decided to cancel the booking at hartz and made another different one. We were then advised I’ll get my refund, to this day I still have not received it. They later asked me to provide them with relevant documents proving that the was money in my credit card at that time, then now turning around saying the was no money in my account so they wont refund. how did we redo another booking same day and get a car if the was no money in my credit card?