A Sim Card is a little,thin rectangular card in all GSM cell phones.It ca be found in the battery compartment,behind the battery on most models.A sim card is your phones' Id.It stores the number that others dial to reach you,as it stores it.You must have a sim card to use your cell phone,if its is removed the cell phone stops working, and your number will no longer be stored.
Subscriber Identity Module (Sim) card is kinda like a memory chip from your PC. You can place your sim card in anothers phone and all charges or debit of the minutes by your cell service provider will be charged to YOUR account ,not the phones owner.Its really not a big techy thing to swap these out. Using an unlocked phone ,you can purchase a local (if traveling abroad)pre-paid sim card giving you a local number wherever you go.That will save you from paying international roaming charges to your service provider back home.
 USB 1/2.0 GSM CELL PHONE SIM CARD READER WRITER BACKUP  US $.99
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 USB SIM Card Reader GSM CDMA Cellphone SMS Backup CA13 US $1.79
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 Double Dual SIM Card GSM Card 13td Mobile Phone Card US $9.65
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 SIM Card Date Reader Backup Device For Cell Phone GSM e US $10.75
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 USB 2.0 SIM Card Reader GSM CDMA Cellphone SMS Backup US $.01
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 New USB Cell Phone Sim Card Reader For Backup SMS to PC US $.01
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 USB CELL PHONE GSM CDMA SIM Card Reader Writer US $.01
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 N98+ Dual Sim Card Dual Standby Cell Phone MP3 Touch US $44.44
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 Quad Band Dual Sim Card Touch Screen Mobile Phone A008 US $62.00
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 NEW UNIVERSAL TURBO SIM CARD UNLOCK 99% MOBILE PHONE US $3.54
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