To see others online without being seen, in the Tools menu, tap My Status and select Appear Offline. If you block a contact, you will appear offline but will remain on the blocked contact�s list. To unblock a contact, tap and hold the contact, then tap Unblock on the pop-up menu.
Chatting with Contacts
Tap a contact name to open a chat window. Enter your message in the text entry area at the bottom of the screen, or tap My Text to enter a preset message, and tap Send. To invite another contact to a multi-user chat, in the Tools menu, tap Invite and tap the contact you want to invite.
Enter message. Tap to send message.
To switch back to the main window without closing a chat, tap the Contacts button. To revert back to your chat window, tap Chats and select the person whom you were chatting with. To know if the contact you are chatting with is responding, look for the message under the text entry area.