Complete disregard for customers

We hired a car from Sixt for our holiday about a month in advance. When we went to collect the car it turned out all their systems were down and had to use a manual method for card payments. We tried various cards and none worked, so we called our banks and credit card companies but all said the manual process that Sixt were using was not secure which is why they couldn't be paid. Turns out that this was a common problem that had been ongoing for 2 weeks, however they decided not to tell customers in advance. Why? Well because then they'd lose all money when customers cancelled and used someone else, whereas instead they waited to see whose money they could take and anyone they couldn't they just abandoned. We offered multiple solutions including paying cash, leaving card details and paying when systems were up etc. But they just didn't care. We were left standed at faro Airport on our first family holiday with a 4 year old and 5 month old for over 3 hours trying to get another car along with multiple other customers who were all in the same position. I will accept technical difficulties happen, however I will not accept that any company can show complete disregard for their customers with no alternative proposal given. I highly recommend staying far away from this company.