I know alot of people are so angry about this problem and i am one of you but i managed to follow this issue inorder to find a solution and finally after alot of work, i managed to find the problems that cause it and found a solution for every case possible.
let me start with the problems that cause this issue.
CASE 1 (SIM Cards): Iphone 4s requires a specific sim card wiring technique different a little bit than before.
Solution 1: Simply contact your carrier and order the newest sim card available. ( 128K better than 64K ) and it case the new micro sim card did not work, order a regular sim card and cut it to the size of the micro sim.
CASE 2 (Carrier Network) : Iphone 4s has 2 antennas giving it the ability to connect to 2 signals at the same time causing the signal to shift from one hotspot to another without cutting the network. but to achieve that, the connection between the two spots must be perfectly synchronized and from the same type ( ex: 3g to 3g or edge to edge or gprs to gprs or 2g to 2g. any light mismatch will cause the phone to lose the signal and never be able to abtain it back ( No service will appear, and you are forced to restart your device or reset network setings ). and unforunately, we dont have the option in the iphone 4s to restrict our device to a specific network type unlike older devices. Im not sure that apple can fix this issue with an update, its the responsablity of the network companies to remove such errors from their infrastructures.
Solution 2: Order the 2g only sim card or a 3g only sim card, and it will work perfectly untill a better solution is found " but both solutions have advantages and disatvanteges. The 2g line will let you obtain a very good signal all over the country but you will not be able to connect to 3g network.
while the 3g line will let you obtain a good signal only in specific areas in the country but you will be able to use cellular data. or if you have a factory unlocked device, you can try to swith to a different carrier
Case 3 ( Iphone Software ): Sometimes, when you udate your device firmware or download any ios, there is a possibilty of an orror to occur without being noticed and that error will not also be noticed during the installation of the firmware, ending up on your device causing fialure.
Solution 3: 1- download latest itunes 10.5.1
2- download a fresh ios 5.0.1 ( from itunes not from iphone device )
3- Go to DFU mode, Open itunes and restore as new iphone (to avoid any remaining traces of previous corruption or error)
4- Go to Settings --> Phone --> Sim Pin and turn it OFF
5- Turn On airplane mode and wait 15 seconds
6- Turn OFF airplane mode
7- Go to Settings --> Carrier --> Automatic ( turn it off and select your network manually )
Case 4 (Iphone Hardware): some series of the 4s and specially the first serie delivered, had a problem in teir sim reader, and to help you more to identify this seire, simply go to Settings --> General --> About and check the model number if it starts with MD2 then you are not lucky and you phone may never work with your carrier
Solution 4: if you have a factory unlocked device, please consider changing the carrier and give it a try 90 % of the times it work, other than that, you must take your iphone back and order a replacement.
I will be happy to answer any question
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