SPAM

• SPAM is any unsolicited message. If a recipient has not explicitly agreed to receive messages (opt in) then you are potentially sending SPAM. If recipients Opt Out either by replying to a message or by any other method then they should never receive another message from you.
  See the Bulletin Wireless Opt Out Process for more information and the wikipedia article here.
  The NZ Unsolicited Electronic Messages Bill can be downloaded and should be compulsory reading for any person using SMS as a marketing or communications tool.