All I have to say is he. No company can guarantee no matter how well the number one natural search positions. The only way you could say this is unethical methods with positioning your website. Of course, most companies use to come pay per click advertising for your site, but you can do it yourself and get the same exact results.
In order to stay on top of natural search, you need to have ethical means to promote and optimize your site for SEO. Be sure to take time to analyze your site compared to the first 10 sites for each keyword top. If you see their sites, compared to yours, correct the changes can be made. This is a great, make sure that no company or individual in your company creates doorway pages on your site.
These inflate the results for a very short time and can and will lead to you being banned from the search engines. There are a lot of companies that say they will put their content on your site to help the results, this means only that they are going to create doorway pages! Do not let them do this, because it will lead to your ruin sites.
Be careful out there with all the companies search engine optimization and then possibly do your own optimization with the same results. You might want to try to find a company that gives only an optimization report that allows you to optimize your site to your liking. Good luck out there!