iphone 4S can't get to Home Screen!!!

Having changed SIMs I am getting the message The SIM card inserted in this iPhone does not appear to be supported which is fine. The instructions from Apple say if this happens restore your phone. Unfortunately I cannot get out of the setup loop going back and forth between wifi and SIM!!! So cannot get to Home Screen in order to access Settings. I have of course tried the hard reset a couple of times (hold down Sleep and Home). Any suggestions please folks?