I am trying to make a simple while loop which reads in a text until the person types quit. And it's not working, and I know it's a rather simple problem I just can't seem to understand... Once again all assistance is greatly appreciated.

#!/bin/sh
astring="z"
while astring!="quit"
do
read astring
if astring="z"
then
astring="hello my name is Gsmith and I have 5 dollars"
echo $astring
else
echo "Never again"
fi
done