Collecting on the SEO Guarantee

I signed up with a SEO Company more than 8 months ago and they have done nothing in getting search engine placement for my keywords. They have a guarantee stating that after 6 months I would get a total refund if they fail to get me placed. It is clearly stated in the Service Agreement.

My problem is how do I collect on that guarantee??. I tried disputing the charges with my credit card company but they said that too much time has passed since the charges. The SEO company does not return my emails or calls. My biggest weapon is giving them negative publicity... where can I go to tell people of my experience with them? Is there an organization on the Internet where I can file a complaint?
What can I do that will help me to get the SEO to honor their guarantee?

This is the third SEO company who has failed to live up to their promises. Are there any legitimate SEO companies out there that will do what they promise?

Yes, there are legitimate companies, and they don't promise exact rankings because that sort of thing cannot be promised.

Familiarise yourself with the Google "Guidelines for Webmasters" and the various things they have to say about SEOs - especially the stuff about "choosing" and "promises". Read the relevant stuff over at Matt Cutts blog too (he is the head of webspam at Google).

You can probably take it up with the Better Business Bureau if you are in the US. They may be able to help you some.

I do not know whats is happened out the field, what i am doing now and proposed to my client is base on Performance.
i.e No Performance, No payment.

Apparently, we will charge the customer a minima "setup" fees, after the respective site or links or URL being listed onto a respective Search Engines with a favorable keywords, then only we will collect the balance.

On the other hand, if a particular customer wish to maintain their ranking, what they need to do was just to sign up our maintanance package which is running the same concept, no result, no payment. Meaning, if the respective month does not shows any result or the ranking drops out to the 4th or 5th pages of the respective , we will not charge them.

Perhaps, you should look for those SEO comnpany who can provide the same solutions. "Charge by Performance".