enterprise rent a car - jacks up rates

i had to rent a small car because my car had a check engine light come up. i took it to the nissan dealership who recommended using enterprise rent a car because they 'worked with them all of the time" and they could bring over or drop off. enterprise advertises we will pick you up free. well i made a reservation using their website, which was erroneous and when i went to pick up the car, they wanted to give me a big car. i needed a car very bad so took the big car, expecting it to be at the lower rate of the small car, which was the size i needed. at the end enterprise charged me a big car rate and also wanted to charge me for drop off at the car dealer, even though i had been told that drop off happens all of the time because the enterprise people are there all of the time. i think they need to be a little more up front about what they do. i had a lot of trouble with this company and the home office promises to straighten it out and then never does. they let you duke it out with local agency. the home office isin the phillippines, where i dont think they understand us very well.