I believe they have to be sent back to be reset unfortunately.
If you are trying to reset admin and engineer dial up passwords you may be able to get in with the root login where the password may still be at the default ship2shore
Once in there, edit /etc/ppp.secrets (I think) and you can reset admin and engineer dial up passwords there.
I havent done one of these for a while so this info may not be 100% correct.