Such data includes user identity, location and phone number, network authorization data, personal security keys, contact lists and stored text messages. Most SIM cards contain between 64-128 KB of storage. A SIM card, also known as a subscriber identity module, is a smart card that stores data for GSM cellular telephone subscribers. Such data includes user identity, location and phone number, network authorization data, personal security keys, contact lists and stored text messages. If you have to change phones for whatever reason, you’re able to transfer your contacts via the SIM card painlessly. Often, a SIM card is provided with the purchase of a phone by your carrier and it is used to store data about your account. That depend upon the type of the SIM. A SIM card, also known as a subscriber identity module, is a smart card that stores data for GSM cellular telephone subscribers. A SIM card is also capable of storing SMS messages and the names and phone numbers of up to 500 contacts, depending on the memory size of the SIM card you have. Because it has a small amount of memory and a very low-powered processor, the SIM card not only enables communication between the phone and its carrier, but stores information such as phone numbers, security data and more. for Example:- In Airtel we can save around 16K of data we can save.