$$$ Problems with Traffic Cash Gold

I'd like to ask you for an advice, here's what happened:

I started sending my traffic to TCG sites at the end of november 2003. I was using regular linking codes for which I was paid 35$ per sale, I didn't even know then that linking directly to join pages is allowed and possible at Traffic Cash Gold (it isn't mentioned on the site). After few weeks I received a check from them for first 2 weeks, but I sent it back - I wanted the money by wire and much later, for tax reasons.
So then in February I asked Laura from TCG if I could link directly to join page, and if yes then how the links should look like (too bad they didn't mention that they pay 25$ for signups from join page links). So in the beginning of February I changed part of my links to direct join page links and after a few periods, with stats still showing 35$ per SU, the rate has suddenly changed to 25$ per SU for current period.

So I asked why is that, found out about the different rates, decided to go back to regular links and asked them to change the rate back to $35. They did change it back.

But then I finally started talking about the wire transfer - I had a new bank account set up at last. And when I asked how much will the payout be, they gave me much smaller number than I calculated. It turned out that they counted all my sales from the beginning as 25$ per sign up!! The difference is more than $20k so it's a pretty big deal to me. :/
Their stats are not too good, they don't show if I'm using regular links or direct join page links (still waiting for TCG 3.0...), they had to change the rates manually.
So when I contacted them it turned out that they ASSUMED that I was using direct join links in november and december (they say their tech. dept. doesn't have logs for those months anymore) because majority of my links were sent directly to join page in January (not true!) and February (that is true)... They are ignoring the fact that the check they sent was for 35$ per sale - well, they're now saying that it was an error and it should be for 25$ per sale...
They still claim that I was using direct join page links in January (and they claim they have logs showing that), but there's no way I was! I found out about the different linking method just in February and not even one direct join hit could appear in their logs in months before that! So something's not right...

Of course they don't want to show me the logs for January, because they can't "disclose confidential information"...

So I mentioned to them the facts - a chat with them where I asked about join page links, a similar post on GFY (both around the beginning of February), the first check they sent me (with 35$ per join), that the 35$ rate was in stats for 3 months from the beginning - they just ignore them, saying that the tech dept. is saying otherwise...

There is also the Wayback Machine http://www.archive.org/web/web.php that could prove that I was using regular links in those months - unfortunately right now the latest archived copy of my site is from October. I wonder whether they would ignore this fact too...

So I'm asking you guys - what are my options? How should I approach the case in order to get the correct $ amount that they owe me?

Any help will be appreciated :/