What is the full form of SIM card? How to call between two mobiles?

What is the full form of SIM card?  How to call between two mobiles?

Sim Card: Nowadays everyone uses mobile phones. Mobile phones were started for calling, with time it became more advanced and today we use its modern form as a smartphone. But, even after so many changes, its main work calling is still included in it. Everyone knows that for calling we have to insert a SIM card in it. You cannot make calls without a SIM card. With the development of technology, the SIM card has also changed its many forms. Even nowadays E-SIM is being used in modern Smartphones. Today…

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