Carrentals.com Did not honor estimate. Change reservation without authorization. Expensive higher price. Currently irresponsive Internet

I made a reservation with Thrifty at Fort Lauderdale via CarRentals.com on July 22nd. for an estimate of $159 (see attached pic.). When arriving at location, on Aug. 19th, I found the reservation was changed to a more expensive car type without my knowledge (went from an Economy car, to a Full size car), implying a total of $43 more. I took the car because clearly I needed it.

Thrifty didn't care, saying reservatons made by 3rd parties is not their problem. They told me I have to "call" CarRentals.com, which I couldn't since there's no phone number contact to be found. I wrote an email requesting a refund of the difference between my estimate and what I paid. They replied an email saying that the reservation was changed on Aug. 17th, 2 days prior to pick up. I checked and the only thing I had that day was a reminder about the reservation. I didn't even open that email because I saw the title and yes, I knew I was having a reservation... kind of hard to forget when you arrive at another city. In that email was the new surprising estimate with a different car.

I did not change my reservation, nobody else did in my knowledge since I'm the only one checking this information. I wrote them stating I don't care how that happened, who did that and how, the only thing I wanted (still what I want) is to receive a refund for the difference between my estimate ($159.37), declared in an email dated on  July 22nd, and the final cost of the rental (203.19 paid on Aug. 25th) which is $43.82.

No answer after several days. Wrote back sending the same email and no answer yet.