i want to replace two phrases in text file

originalstringA.1.
blah blah....
originalstringB.1.

got this code so far:

#variables
IP=$1
NO=$2
FS=$3
IS=$4
NN=1
#echo variables
echo ''
echo $IP
echo $NO
echo $FS
echo $IS
echo '****'
echo $NN
#generate files and configure
while [ $NN -le $NO ]
do
cp template.egsinp $IP.$NN.egsinp
sed s/template/$IP.$NN/ <template.egsinp > $IP.$NN.egsinp
#i need something else here that replaces something else and has the same input/output files as the above sed.
echo '****'
NN=$(($NN + 1))
echo $NN
done
#exit
exit