You may not be able to change how jw's behave or if they collect personal data, however, if the public knew that they kept a record of each conversation at the door people would simply quit talking to them all together.
I'm in the US and when people find out that the jw's will take notes to share with the cong about their conversation they were horrified. I told them that if you mention you were divorced, what religion you are, how many children, spouses name & occupation, etc... they will take notes and it will be noted for your address they couldn't believe it!
I saw some notes my jw took out in service one time, creepy! they are like stalkers.
Publicize, publicize and publicize some more.