Possible Duplicate:
What is a good way to get many inbound links to your site?

I'm probably taking a huge chance here, but I've become a bit desperate. We've paid many a dollar to companies to help push up our page rank, but with no results. I myself have tried everything. Page Rank got up to 5, and now it seems to have gone down to 4. Any advice, even if you point me to an AFFORDABLE and RELIABLE company, I would really appreciate it?