URLs go to wrong sites

[chaloum]

Ive got a strange issue where the urls go to the wrong sites.

Example: the server is: Mysite.com

I have a client and site for Mysite.com this being the servers main site. So ther server is Mysite.com and the domain for the website in Mysite.com

I have other sites configured via the server is Mysite.com and the domains are for example
Site1.myothersite.net
Site2.myothersite.net
Site3.myothersite.net
Site4.myothersite.net

Now in the browser if I type Jim.mysite.com it goes to site3.myothersite.net

No matter what I use to create an URL to a site that doesn't exist it defaults to site3.myothersite.net

Other Than the server name there is no relationship between the sites, site3.myothersite.net and Mysite.com

I don't understand why it goes to site3.myothersite.net instead of Mysite.com


How do I fix this as its no good this way