Dear,
You can go to SM37 -> give the Jobname or put a * in the Jobname and give your user name and execute.
It will show the list of jobs scheduled by you and choose the relevant job and go to Job from the Toolbar and select "Cancel Active Job" (CntrlF1)or if you want it to be permanently removed , click on "Delete"(ShiftF2) from the Job Menu.
Regards,
R.Brahmankar