I would say that the easiest way for you to do this is to check in and print your boarding pass at a Check-In kiosk. If you press the frequent flyer number button you can change it to an alternative.

The entry to remove a frequent flyer number in DCS is 1/M/ but it will be very very rare for you to find someone who uses DCS these days as most use PRS which is a user friendly front end system to DCS.