A SIM card is a small, removable card or chip that contains your mobile account information and is interchangeable between all GSM phones.


If you use a SIM card in your mobile phone, the phone is a GSM device; otherwise, if your phone does not require the use of a SIM card, the phone is a CDMA device.;
, This step can be performed if you are unsure if the phone requires the use of a SIM card.


Open the battery compartment of the phone. The SIM card holder is normally located underneath the battery; however, some mobile phones will have a SIM card slot or tray located on the outside of the phone.






Remove the battery from the phone and inspect the inside of the phone for a SIM card or SIM card holder. Most mobile phones will have an icon or picture that depicts where the SIM card should be placed.






If you need assistance with locating the SIM card slot, or determining if the phone requires the use of a SIM card, consult with your phone's manual or contact the manufacturer of the phone.






If you use an iPhone 4, the GSM model will contain a SIM card tray on the right side of the device; whereas the CDMA model will not have a SIM card tray.
Determine if your phone requires a Subscriber Identity Module (SIM) card.
Check the inside of your phone for a SIM card.
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