you could bypass waiting for the next jw caller,
send the hall a registered letter (that they have to sign for that gives you proof of delivery) put in it your name and house number and state that you wish to be put on their no call list immediately,
say that you will view any further calls as harrassment, and that you are prepared to use legal means if it is not adhered to.
cc. your solicitor on the bottom of the letter.