PHS shows whether the other party can receive the failed transmission.

After you send a short message yourself, the server receives your signal and sends it out. At the same time, the server also sends a signal to your communication tool, so he will show that the transmission is successful.

But if it's because

1, the signal is bad, and the server doesn't receive your signal, so your communication tool doesn't receive the signal from the server, and it will display-sending failed.

2. If you owe money or the server thinks that your communication tool has stopped serving, then the server receives your signal, but does not send you information, and sends a failure signal to inform your communication tool, then your PHS will display-send failure, or simply do not send a signal to your PHS, and your communication tool will display-send failure after waiting for a long time.

Unless there is something wrong with your communication tools (China Unicom)