Q: my sim network is not showing ???

I use iphone 4s ..... suddenly this is not showing my network even though it is showing 'searching'. In setting it is showing that I am using my sim . I have used other sim card to check but the result is same . when I used it without sim card it is still showing 'searching' where it should be showing NO SIM . whenever I try to call someone they can receive my call but I cant listen anything even him . then when I try to cancel the call it just hanged and I have to restart the phone app . And when others call me my phone dont show anything .