Rental Cars deposit more than triple

My husband was trying to make a booking right before his flight and due to misinformation on the website we couldn't amend the booking in time and now have lost the rental fee. The website functionality is horrific and clicking on certain links don't take you to where you need to go and no solution is given. The links do not lead to the expected page at all... The "live chat" also doesn't seem to work. He tried phoning the helpline and couldn't get an answer. He did NOT pick up the car due to misinformation on the deposit amount and he wasn't able to cancel it at the airport pick-up. We will fight until our money is paid back into our account. The previous cancelled booking was also deducted from our account and now we have a massive cashflow problem, with two cancelled bookings deducted from our account. What a ********** website with links all over the place and no proper functionality or user-friendliness. The deposit communicated to us over the phone was more than triple when attempting to book online via rentalcars.com. We demand a full refund of our booking fee.