What software uses traffic to send text messages?

Download and install the "Youni has you" software. When entering a message, the button on the right is a charge message if it shows "Send", and a free message if it shows "Free"; When a short message has been sent, the words "short message" will be marked below, which is a charging short message.

E-mail seems to work. It can be sent to the other party's mobile phone number for free, and there is a limit on the number of short messages.