I completely agree with Diobach. It sounds like the links you were buying weren't worth much in the first place, and it's good that you've decided to stop using them.
Link building has to be very targetted to be effective, just adding links to directories no longer works. It's very easy to get links from directories, especially if you pay for them. Google knows this, and so places little value on them. Originally, the link system was supposed to be on the basis that if someone adds a link to you, then your site must be a valuable resource and so could help other people. However, the system was massively abused, and it meant that having a link to your site couldn't guarantee the sites content at all, especially when it came down to how much you could spend rather than how good your site is.
There are loads of
SEO tips on this forum, so read everything you can and put them into action yourself. If you decide in the future to hire someone else to do your
SEO, then ask for recommendations here first. Unfortunately it sounds like your
SEO company has taken a lot of money for doing very little.