Html website page redirection according to domain name?

there I have a website with 2 domains pointing to the same IP address. One is a (.com) the other a (.co.za) The entire site is the same for both domains but I would like to be able to direct traffic to different contact pages according to the domain that they have used. For example, if they got to the site using (.com) I would like them to see my American and Canadian contact details (which is on one page). But if they got to the site using (.co.za) I would like them to see my South African contact details which I would like to be on another page not showing the American and Canadian details.

Could anyone please advise me on the best way to get this functionality.

Thanks