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The user and administrator guides are available on the Xerox 7556 Support site
I would suggest that you review the Faxing section and setting defaults in the following to determine if these could provide a solution.
User Guide - WorkCentre 7500 Series or System Administrator Guide
If that does not resolve your issue you may consider contacting our specific product support experts at the following link:
Fast Track to the Expert
Xerox Customer Tools & Social Media Moderator
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