Total script as below

#!/usr/bin/ksh
#####################################
# Starting the Main Script
#####################################
set -v on
set -x on
ScrName=`basename ${0}`
NOW=`date`
echo ${1}
echo ${2}
#
#-------------------------------------
# Routine for ERROR HANDLING
#-------------------------------------
#error_handle ()
#{
#echo "----------------------------------------->"
#echo "${NOW} ${ScrName} Error Handling...!"
#echo "----------------------------------------->"
#echo
#echo " ERROR Occured while ${1}"
#echo " EXIT from the program ......!"
#exit 1
#}
#--------------------------------------
# Check Command line arguments
#--------------------------------------
if [ $# -ne 2 ]
then
echo " ${NOW} ${ScrName} : Invalid Parameter list..."
echo " ${NOW} ${ScrName} : Script needs TWO parameters"
echo " ${NOW} ${ScrName} : Param1--Input file path"
echo " ${NOW} ${ScrName} : Param2--Output file path"
exit 1
fi

#--------------------------------------
# Get Log Directory
# and populate Log variables
#--------------------------------------
LogDate=`date "+%Y%m%d"`
LogDiry="${2}"
LogFile="${LogDiry}/SELUPD_${LogDate}.log"
#--------------------------------------
# Automatically Redirect STDOUT and STDERR to log file
#--------------------------------------
exec >${LogFile}
exec 2>${LogFile}

//////some logic
done
set -v off
set -x off
exit 0
#####END OF THE SCRIPT##########

i am calling the script as
sh script_name /home/user/work/infile /home/user/work/outfile

even i tried with the following calls
ksh script_name /home/user/work/infile /home/user/work/outfile
script_name /home/user/work/infile /home/user/work/outfile
./script_name /home/user/work/infile /home/user/work/outfile

but no use.

if i issue the command , echo $SHELL, it is giving the output as /usr/bin/bash.

I tried to login into ksh by issuing /usr/bin/ksh and called the script, but no use.