Invalid Sim Card?

A few days ago my iPhone 4s suddenly started displaying the message 'Invalid SIM' on place of my network.I have tried all of what apple have recommended, taking sim card in and out, airplane mode, resetting network settings etc. I updated to iOS 7.0.3 earlier today, hoping this would resolve the issue as I had similar problems when iOS 6 first came out, but the issue still persists. Anyone have any advice?

I see the only other option to be to replace my SIM, but as it turns out, my provider no longer manufacture SIM cards for the iphone 4/4s, so that is not possible. Help