This would be relatively complicated and require quite a bit of hand coding.
An easier way to do this would be to have a page with links to the different ways to be contacted where each link will go to a page that has the form to collect the information needed.
Another way to do this would be to have a radio button group/select list with the different options and submit to another page with the forms and only display the form that the user selected and keep the rest hidden. Each of the forms would have a submit button, so only the validations on that form would be used.
