IPhone gives me the No SIM Card Installed message. What do I do?

I just transferred my SIM card into a friend's iPhone 4, and it says that no SIM card is installed. How do I get it to work?

For the record, my sim card is a T-mobile SIM card that worked just fine in my old phone (which was an iPhone 4S).

Buy Samsung Galaxy S III.
That should fix it

The sim card will not work if the phone is lock to different net work or if is not insert properly it will not work so clean it and insert again

Is your friend's iPhone on tMobile also? If its not, it will not work.

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