Is there really a software called "Fetion" that can send short messages for unlimited free?

It's true. The interface is similar to QQ, but you log in with your mobile phone number (only for China mobile users). After logging in, invite your mobile friends. If the other party agrees, you can send short messages on the computer in the future, and there is no charge for unlimited sending.

Note: Fetion client is free, but Fetion function of mobile phone is free.

So you just need to open Fetion on the client.