Will Call is Guest Realtions.
Guest Relation Windows open 30-45 minutes before the parks (including AM EMH.)
Guest relations can be found just outside and inside every theme park, and the Transportation and Ticket Center at the MK parking lot, and at the International Gateway at Epcot.
Also, at the gates of the water parks and at two locations at Downtown Disney (Marketplace and West Side.)
You can also deal with most ticket matters (other than Annual Passes) at the lobby concierge desks or ticket windows at all the WDW resorts.