How to get rid of duplicates?

Hi,

Well, the thing is that it's actually not the same page.
This is the contact page for the product with the id 4392.
You'll have different links with different ids in it, one for each product.
And we can't by default say that the contact form should not be indexed or say which URL should be the main one for that form (using a canonical tag).
Basically, there is no one size fits all solution for this issue that we could add by default, as far as I know

For your case, where you don't even want to index that page since it will always be accessed from the product page of a product, you can add that code at the top of the product / contact.php view file via the menu Display>Views:

<?php
$doc = JFactory::getDocument();
$doc->addCustomTag('<meta name="robots" content="noindex">');
?>