Got given wrong car, Thrifty blamed Authentik

Before arriving at Canada I was impressed with Authentik’s prices and customer service. However, we ordered a sub-compact car, and on Authentik it stared ‘chevrolet Spark or similar’. However, when we picked up the car it was a compact type car - a Nissan Sentra. We went back into the office and said it wasn’t a sub compact car, it was too big for us. They said that Authentik had told them to give us a compact car, and showed us the computer screen saying compact. We asked to be changed to a subcompact as we are fairly young drivers used to small cars, but they said they didn’t any left. Therefore we had to go ahead with the larger car, which made us nervous. We are unsure whose fault it was, but it did put a stressful twist to the beginning of our trip.