Is there a word regarding boys and girls exchanging indecent messages via mobile phone?

The messages received via mobile phones are akin to restroom graffiti, which are filth and the words of those who lack understanding. It is strange that their numbers appear with their messages, and sometimes they contain a form of polytheism (shirk) with Allah. Therefore, it is obligatory to advise the users of these messages and remind them of Allah and the ruling on what they are doing, and that they may fall into the category of those who spread indecency among the believers.