Downgrade - rentalcars.com does not guarantee car category

In May 2021 I booked a Toyota Corolla Sedan with rentalcars.com. At pickup time the local company in Greece informed me that they have a Nissan Pulsar instead. After 15 minutes of convincing them that this is a downgrade, I was left with a choice: go to another company and lose time and money or take Pulsar. So for 30 days my 4-person family had a cheaper, smaller car with smaller engine than the Corolla we paid for.
I thought that after the rental we'll be compensated, at the very least returned the price difference between a cheaper Pulsar and Corolla we paid for. I mean, the Pulsar was a lower category car on both rentalcars.com website and in the local company's brochure. But no, rentalcars.com customer service only offered 5% discount for future rental!
The worst is that the local company doesn't even have Corollas in their fleet. I was just tricked by rentalcars.com with a nice Corolla Sedan photo.