@wtran88
A misaligned SIM card. The shock of impact, such as when you drop your phone, can cause your SIM card to move in its slot and prevent your device from reading the embedded chip. To test whether your SIM card is misaligned, turn off your device and remove the SIM card. Reinsert the SIM card and turn your smartphone back on. If the SIM card was misaligned, your device should now be able to read the SIM card and connect to a mobile network.
A damaged SIM card or a malfunctioning smartphone. Checking whether your SIM card or your smartphone is to blame for your connectivity issues requires access to another smartphone, one you know is working properly. Turn your smartphone off and remove the SIM card. Insert the card into the alternate smartphone. If the second phone is also unable to read the card, your SIM card is to blame for your issues -- either because it is dirty or damaged
