Information is forwarded by SMS.

The retransmission of short messages may be the problem of the sender or the receiver. Short message center is used to send, receive and charge short messages. Check the bill to see how many items were charged at that time. If it is charged by multiple items, the problem lies in the delivery link. It is likely that the mobile phone did not receive the response message correctly after the short message was successfully sent to the short message center. Then, the mobile phone will handle the unsuccessful SMS sending and send it repeatedly. In this way, in the short message center's view, if a mobile phone sends multiple short messages, it will be charged according to multiple short messages. If it is charged according to a single bill, the problem is that it is easier to receive, that is, after the mobile phone receives the short message, the short message center does not receive the returned confirmation message, which causes the short message center to resend it to the receiver's mobile phone. According to the SMS center, the sender only sent one SMS, so he will only issue a SMS bill. According to the description in the question, many students have appeared, not limited to a certain person or a certain type of mobile phone. The problem is likely to appear in the signal quality of the local operator's base station or the software bug of the switch.

Please accept it, thank you!