Redirecting site from WWW to non-WWW

Hi,
We built our website on WordPress on Yahoo Small Business Hosting.

We want to redirect http://www.domain.com to domain.com (without www). I need some help on how we can do it (without using .htaccess, as Yahoo is not giving access to it).

I already tried php redirection but it did not work out. I also used Redirection plugin, which didn’t work out too.

Thanks in advance.