Ack! Hosting and Domain problems - please help!

So I signed up for a hosting deal had over at slickdeals.net. I got hosting through Cookiehost. I have 2 domain names registered with Hostmonster. I went in and changed the name servers on them to those provided by Cookie Host. All is well there.

The problem is that, when I bought the Cookie Host hosting, it required me to provide a domain name, even though I wasn't purchasing one through them. So I did, but I hadn't registered my other 2 with hostmonster yet, so I used an old one I had (though it never asked for any verification that I indeed did own that domain).

Now all the options/accounts/prefs of my CookieHost info is tied to that erroneous domain that I provided. It uses cpanel - and it seems that the "main domain" has been set to the bad domain. How do I change that main domain?

An example of the problem is this: when I am trying to set up FTP access to my new domains that have been routed to my cookiehost hosting, the manual settings look like this:
login: DesiredDomain@BADdomain.com
FTP server: ftp.BADdomain.com