An iPhone 4 may be a high-end device but even such a device can confront you from time to time with 3G connectivity problems that prevent you from making/receiving calls and using wireless data. Sometimes these problems are accompanied by a “No SIM card installed” error message. What your Apple smartphone is trying to tell you via this message is that it is unable to recognize the SIM card. This message also results in the replacement of the carrier’s name and the signal strength bars with the words “No SIM”. However, even if the situation looks bad you shouldn’t be too worried because most of the times the problem is caused by the need to reseat the SIM card. That’s because during smartphone use the SIM card can easily slightly dislodge.
If order to see is the SIM’s location is causing the problem you should first locate your iPhone’s SIM card slot. This slot is actually easy to find because it’s placed at the top of the smartphone, between the Hold button and the headphone jack. On the exterior you will see a tiny hole, but the interior actually hides the tray where the SIM card needs to be placed. To reseat the card you will have to use an unfolded paper clip that will help you use the slot’s hole in order to pop the tray out. You should then make sure that everything is in place and push the tray back. If everything goes as expected you should regain 3G access in a matter of minutes. If for some reason the usual carrier name and signal strength bars fail to be displayed, you should eject one more time the SIM card and make sure that no dirt is affecting it. You can do that by blowing but it’s best if you use a shot of compressed air. If the problem was caused by positioning and dirt these actions should get back 3G connectivity.
If even after you clean the SIM card tray you still find it impossible to make calls because of the “No SIM card inserted” message, you should consider testing the SIM card for malfunctioning. That’s because this is the next logical explanation. A simple way to perform a test involves locating another SIM card that you can guarantee it’s functional and insert it inside your iPhone 4 instead of its usual SIM card. If with the new card the signal strength bars are displayed it means that your iPhone’s original SIM card is no longer working properly. In this case you need to visit the closest Apple Store in search for technical support and a solution that will help you keep the number.
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