I am having a problem with this form

[tane]

I am having a problem with this form hoping was someone can help whith the radio buttons for Preferred Method of contact on my form email and phone i carnt work out if they click email but then change thier mind to phone the email radio still is clicked i was wondering if someone could tell me how to stop that below is link to the form i need the help with
http://theweddingcenter.com.au/mailing_list.html

[Fang]

<div align="left" class="style179 style93">
Phone <input type='radio' name='contact' value='phone' />
Email <input type='radio' name='contact' value='email' />
</div>