If you do not wish to take part in the survey or donate to the charity etc, the best response is to say "No thank you." and walk away. Remember you are under no obligation to buy or give. They should not chase you down the street, shout after you, or block your path.
If you do experience such behaviour you can make a complaint to the company or charity who they are representing. You may need the name of that person. Most workers work for third-party agencies that have contracts with charities.
If you think the person is a bogus charity collector, tell the charity or report them to your local police.
If you do stop then you should be told that they are being paid for collecting on behalf of a charity.
For further information, please visit the website in related links.