I thought of this as well. But after looking at it a little deeper, if it was an option in the PM box area on the in game phone I don't see it being that big of an issue. After sending the "initiation" message if the phone went away that would help with people spamming it. If someone really wanted to they could copy and paste an initiation text and be doing essentially the same scenario as your describing. Its a huge waste of time especially because I believe after a message is sent via the phone, the selected person you are texting gets reset to whoever is on the top of the list of players.