You can't get rid of the number. It will stay there until another number gets put in. Perhaps CS can give you some codes, but I wouldn't count on it. I have recycled phones at the AT&T store, and nothing happened. Perhaps you could go to a Verizon store. At least these are reputable and monitored.
Also cell phone recycling places wipe the phones anyway, for that reason. Contact your local/county/state recycling facility or call your local Best Buy and see if they have cell phone recycling and just drop it off there.
Also cell phone recycling places wipe the phones anyway, for that reason.
I'm not sure that this would happen with most tracs and n10's. To wipe a fone, with anything other than an option in the fones 'menu', would require having the ability to connect to the fone with some other software - which is normally not possible with a trac/n10 handset.
Trac CS can give codes to change the number on a cdma handset. Maybe they have a set of codes to zero out the fone number. However, if they do, I am sure it would be virtually impossible to find this out.