Why can't Apple's 5s Unicom card send short messages?

According to the situation you described, the reason why you can't send a short message and how to deal with it: 1, the number of the mobile phone short message center is set, so it is recommended to check whether it is set correctly; 2. The system is busy during the peak period of holiday SMS sending, so it is suggested to try again later or avoid the peak period. 3. The sending format is incorrect. If you send a short message to PHS users, you need to add the area code before the number; 4. The SMS inbox and sending box are full; 5. Query whether the SMS function is turned on. If the above situation has not been solved, it is suggested that you can contact the local manual customer service for handling.