One web site owned by dyndns is pointing to my server main ip address. this result in when you type www.siteownedbydyndns.com it show my web site content! i contacted them but they refused to point their domain to elsewhere as they said I don't own the ip my hosting own it! any advice?
Use htaccess to redirect incoming traffic from that url to their competitors site. Then ask them again to please drop your IP from that domains dns. If you pay additional money for that IP as an addon, also let them know. If all else fails, contact your host and request that they inform dyndns to stop pointing that domain to your IP.
Yes or complain to Dyndns's upstream provider that a client of their's is attacking your webserver after already being warned to cease action.