I just went to the business hall and changed my SIM card for free. My mobile phone shows that I am sending a message. .

Don't worry, this information is generated because you need to automatically register for network activation when replacing 4G cards; The message itself is free, and only 1 message is sent. If you continue to send it because of previous automatic activation failure, many messages may be generated. If this is always the case, it is recommended to bring your ID card and card to the business hall for free activation.

Extension of related knowledge points:

SIM card is the abbreviation of (subscriber identity module).

GSM digital mobile phones are also called subscriber identification cards and smart cards, and they must be installed before they can be used. Digital mobile phone customer information, encryption key and user phone book are stored on the computer chip, which can be used to authenticate the identity of GSM network customers and encrypt the voice information when customers talk.