Will the new mobile card change its number? Can the old card be used after activation?

Before the new card is activated, the old card can be used, but once the new card is activated, the old card will be invalid at the same time; This is because each sim card has only one unique card number, and one card cannot be used twice, so the card will be invalid; Moreover, the phone and text messages stored in the old card are no longer visible, so it is best to back them up in advance.

The sim card is (subscriber

identity

model

Customer identification module), also known as smart card, user identification card, gsm digital mobile phone must be equipped with this card to use. It stores the information of digital mobile phone customers, encryption keys and other contents on a computer chip, which can be used to authenticate the identity of gsm network customers, and uses the sim card for the voice information when customers talk, thus completely eliminating the eavesdropping behavior of parallel calls. The sim card is made in strict accordance with gsm international standards and norms, thus reliably ensuring the normal communication of customers.