How could you even verify if they are working at selling your car? As long as you have your car ad on kijiji/autotrader and craigslist, there is nothing more they could possibly do for you, in my opinion.
I also got a call from one of the above agencies. I continuously asked what the other sites/publications are that they use, he could not give me one answer. Just kept pitching how they work "closely with other dealers for people looking for your car" and how they "offer financing" for the potential buyer. I told him I would take a look at their website and get back to him, but did not plan to. He called me everyday for almost 4 weeks. (I always missed the call as I would be working.) They eventually gave up.
I do hope, somehow, you are all able to get your money back.