Is it true that mobile phones send text messages and pictures for free?

Don't worry, there is no such function, only smart phones can, but if smart phones want to send SMS, MMS and voice messages for free, they must also download related communication software, and the premise is that both of you must use this software, and both of you must use smart phones, and both of you have downloaded WeChat or Uni SMS ... (There are many mobile phone software) You can send messages for free, but at least you need traffic. If you really don't want anything, it is impossible to send messages for free in this world.