just remove the startup script from your rc directories, or it might be a simbolic link to the script, not sure how the /etc directy structure is for that distro. with ubuntu and a lot of other distros you'll have a series of directories
/etc/rc?.d replace ? with 0-6 and you'll have simbolic links in each directory to services that get started or killed for that run level, usually named S??sshd or K??sshd depending on wether that serves should be Started or Killed for that run level. the ?? will be a 2 digit number, is is just in references to order of precidence. change the S??sshd to K??sshd and it will stop the sshd in that run level, i'm guessing you don't want it in any run level show change it for all of them.