What is the ruling on using network messages to add personal matters that do not displease Allah, knowing that the purpose of using these messages is for personal reasons?

If you use the Da'wah Network messages for your personal purposes by writing private things in the section designated for the sender's name instead of your name, the network does not object to that, provided that unlawful matters are not written, according to the terms of use. Therefore, there is no sin upon you.