Funnily enough, I'm in the process of writing to complain to them at this very moment. They seemed to offer a fantastic deal on a car rental in South Africa recently, but my final bill from Budget Rent-a-Car, who turned out to be the firm for which they were acting as agents (which I only discovered when the contract had been finalised), contained a much larger set of extras than I was expecting. I suspect the eventual bill was greater than if I'd simply dealt directly with Budget.
The culprit was the one-way fee for picking up the car in one location and dropping it off in another. I knew I had to pay it, but I was under the impression that it was included in Atlaschoice's quote. Turned out it wasn't, hence the nasty surprise with the final bill.
The rental itself went without a hitch, so my advice is to make absolutely sure you know what's covered by Atlaschoice's quote, and what additional costs you will incur at the point of rental.
Hope this helps,
Charlie