Because not all the sizes are used for the first time, many will be put back after they are sold.

Maybe the previous owner was in business, online sales and so on, so many people know this number.

SIM (Subscriber Identity Module) card is an IC card held by mobile users of GSM system, which is called subscriber identity card. GSM system identifies GSM users through SIM card. The same SIM card can be used on different mobile phones. GSM mobile phone can only be used on the network by inserting SIM card? [ 1]。

SIM card is the key for GSM mobile phone to connect to GSM network. Once the SIM card is removed from the mobile phone, the mobile phone will not be able to enjoy all kinds of services provided by network operators except emergency calls. SIM card can not only be used as a key, but also provide a lot of convenience for users. Users only need to insert or embed the SIM card into any GSM terminal to realize communication. SIM card also manages a lot of business information provided to users, which can be used to store short messages, especially those received when users are away? [2]。

20021May 12, the Ministry of Industry and Information Technology held a video conference in Beijing to prevent and control telecommunication network fraud, strengthen the risk remediation of key businesses such as telephone cards and Internet of Things cards, and accurately rectify the illegal transactions of "telephone cards and Internet of Things cards".

SIM card _ Baidu Encyclopedia (Baidu)