The easiest way is to sell stuff that does not have so much competition...Remember there are probably 100s if not 1,000s of other trying to do exactly what you are trying to do in Google.....
What they are most likley doing is giving you back links from sites they own so when you quit paying they will remove all the back links that made you site jump up and it will then drop back down.
You should go get a lot of back links now yourself before they take them all away so you do not drop back down much.
They also might be feedding your site to many social sites and can go in and remove all that to but you could do all that your self to.
I find it funny that people will hire a SEO company that will do all the things others say you should not do but that is how a SEO company has to do it if they expect to get any results.
On page optimization first
Back links and then
Lots and lost of social sites most all set up just for this reason
They maybe some internet news storys about you but that dose not work as good as it did in the past.
Find some that has a lot of websites all wordpress sites and get them to let you post a blog post about your business on all the sites with a link back to your site .. this what the seo companys do to they with have a few hundred sites they own just to post info on for people that are paying them.
Be your own SEO company its work but as you learn it it will pay off and they as you see how it all works i bet you 100% change all your marketing and even some products you sell. Most people never get it and keep making websites that no one finds.