In case some are not aware of this:
If you want to cancel your orders (or do anything else related to your orders), why don't you log in to the Portenzo "Your Account" page:
http://shop.portenzo.com/login.asp
Once logged in, you can, among other things:
review orders, track packages, change shipping/billing addresses, change quantities, cancel orders, return items (etc, etc)...
If you want to make changes to an existing order, I think the best way is to use the Portenzo customer support page:
http://shop.portenzo.com/help_answer.asp?ID=17#239
Placed my order on March 24th. Used this form to request a change on March 27th, received an acknowledgement about my change request on April 4th.
I couldn't change my order once it went into "processing", which it did fairly immediately.