The WC7556 - WC7556/P are no longer current products.
Sales very quickly "forgets" details about previous generation models.
Somewhat understandably, their attitude seems to be along the lines of "ask someone else, that's not in my job description". Their direct responsibilty is current new models.
I couldn't find anything that shows the difference between the WC7556 and WC7556P. Typically the P just stands for printer. I would suggest calling into our sales department for more assistance @ 1-800-ASK-XEROX.