Why take out mandatory coverage when renting a car in Spain which I had already taken out when booking?

Questioner

I was obliged to take out full coverage insurance again when picking up the car from the Alicante rental company, I had already taken out/paid for this extra insurance with booking.com. Response: but not with us. Pay €315.00 or no car. The keys were waved behind the counter and my credit card was requested. No payment... no car so no choice. Response from booking.com was 'you should have contacted us on the spot'. Nice response, no mobile reception at the airport! I have been emailing back and forth with booking.com for 4 weeks now, but they completely ignore the fact that booking.com guarantees that with car rental + full coverage nothing else is needed when picking up the car and that the extra insurance can be refused on the spot. This is therefore not the case. Any advice on what to do next would be useful. I do not want to leave it at that. The rental company does not fully inform the customer and then makes an excuse. I have simply been ripped off. Thank you very much, I hope for a response, kind regards

Lawyer

Very annoying and it is also not right because you are then double insured. You were allowed to rely on the content of the booking agreement on justified grounds. Then you have to ask yourself whether a bad review is not more satisfying than conducting a procedure compared to the costs (which you will not be reimbursed 100% even if you are right). If it is a matter of principle, then it is different and you can send me an email, then I can help you better and provide information.