SiteGround Web Hosting for domains, Internet

I had a domain, Pelourinho.com, being hosted at SiteGround servers.
Some days ago (12 / 15 days), I entered the site administration area, through this URL
https://www.siteground.com/ua_files/index.php?content_id=99961
and there was a place where I was able to cancel my account: Billing - Cancellation
at some point it asked me if I wanted to cancel immediately or at the end of the contract.
I choose at the end of the contract (Dec 26th, 2009).
after clicking all I had to click... didn't get a confirmation...

as I know that some websites are tricky and some times on purpose... and as I have gone through these kind of tricks, I tried to delete my credit card info.
their site does not have that option...

I said to myself... this smells fishy... so I change the expiration date, to a false expiration date...

Today, Dec 11th, 2009, I received an email saying that my hosting services were renewed. 

As my contract ends on Dec 26th, I got in contact with tech support, then with billing... without success... they refuse to refund me and cancel my hosting services.

is this a ripoff or what?