Iphone 3GS gives "invalid sim" error message

[Cordell]

Hi friends,
I am new to this forum. I recently bought a cool new apple iphone 3gs. It is very nice phone. Two days ago I upgrade my mobile and after that the problem started. From that day my iphone repeatedly gives "invalid sim" error message. I don't know why my Iphone 3GS gives "invalid sim" error message. Anyone else having the same problem.
Please help me.

[Simond]

It seems that you have you have unofficially unlocked, i.e. jailbroken your iphone and that's why you are getting such type of problem. In this case you have to remove jailbreak from your iphone to over come this problem. If you don't know how to remove jailbreak from iphone then use following step.
Just connect your iphone to iTunes and update your iphone's software.

[Halina]

I think there is some problem in your Sim card. It may get corrupted or get damaged and that's why you are getting such type of problem. When you use your SIM card more than 2 or 3 years it become unusable due to it's rough use and that's why your unable to recognize it. For this reason your iphone gives such type of error message. In this case you have to replace your SIM card to fix this problem.

[Lambard]

Have you restart your iphone 3gs? If not, then first restart your iphone. Most of the people face such type of error message and they are bale to fix this proble by performing restart process. It is very easy process. Just turn off your mobile for few minutes and after some times again turn on your mobile. After this you will not get any problem.

[Deep23]

I also had the same problem. I tried various method but none of them worked out. I tried reset my mobile and I restart my mobile but none of them worked out. After this I restore my mobile and Now I don't have any problem. I think you also restore your iphone to fix this problem. If you don't know how to restore your mobile then use following steps.
First connect your iphone to itunes and click on restore button. After this you will not get any problem.