Can you find out who sent a textfree message to a cell phone

Not sure what you mean when you say "text free". The only thing I can assume is that you are either talking about a text message that appears not to have any text, in which case your cellphone should just show you the number like any other text message. Or, you are talking about some website which people text from. In which case they are not required to enter an actual number and there is no way to tell what their actual number is since the website that is sending the message doesn't even know.