Domain forwarding can be accomplished on several different levels. So you have have to do some digging.
First I would check where the domain name is registered. Log in to the domain registrar account manager and see if you can find an icon/tool for domain forwarding. If it is set there, you will see it.
Once you turn this off, it may take some time for the change to take effect. (few min to hours)
If that didnt work, and If there is a web hosting account set up for the .com, the redirect could be handled in a .htaccess file. This file will be in the root directory. Open it up in notepad and see if there is some code something like this:
301 redirect index.html www.some.us
delete the redirect and re-upload the .htaccess file.
If that doesnt work and there is a web hosting account set up for the .com, open up the index file and see if there is some code doing a redirect. it may be a meta tag, javascript, or PHP code. Delete that line and reupload the file.