Unfortunately that is not always the case. Some organisations, particularly those trying to get money out of you, do not pay any attention to such returned letters. To a certain extent one can understand why: if a person who does owe money, etc. could simply stop the demands by just sending back letters, it would be a lot easier to dodge ones debts. Some companies will accept a reasonable explanation of the situation from a householder, but others seem to be unwilling to do anything unless they are supplied with a new address for the miscreant.