The phone rings and a sales pitch starts at the other end making one feel like hanging up, actually more often than not that's the best thing that one can do. Often the stock phrase 'I am not interested' said in a matter of fact way would work wonders and all potential troublemakers would back off nine times out of ten.
However if one encounters a particularly brash and charming salesperson it often becomes a bit difficult to wriggle out of the situation. In these situations no excuse would work, a brusque sentence like 'I am busy' or even a terse 'wrong number' and then hanging up is often the only way out. If one would like to avoid these calls one rule is whatever happens one should not prolong the conversation and divulge any personal details like name, occupation and the like which would make it difficult to hang up and also may result in repeat calls; any offers made on the phone that may sound too good to be true would be just that in reality. Another option would be to contact the telephone company and go for an unlisted number.
You are on their list, and they won't stop to disturb you. You have to verbally tell them to take you off their list,and they aren't allowed to call you anymore.