Beyond Bad Communication Skills

I booked a car with Rentalcars.com through Bookings.com and what a pain. All went well and I got my booking, thank you, but then I wanted to add dates and then came the disaster. I struggled to get the booking confirmed. I emailed Rentalcars.com and struggled endlessly to get replies. The only way you can contact them is by email. The phone numbers on the internet gets you nowhere. Rings forever and nobody answers. Then a deduction just went off my credit card. I can only presume it is for the extra days, fine, but what about asking if this is in order and this is how it works and this is what is going to happen. I still had no response to my email. I finally got hold of the company through whom I will be hiring the car and confirmed my booking directly with them. They can also only communicate with them by email. I will never use Rentalcars.com again.