Hi Bob, it has nothing to do with your phone and everything to do with your SIM card. Is it possible for you to take it out? If so, then do it. Especially if you can replace it with a backup SIM or something. If this isn't an option you'd like to try, you need to find the PUK code for your SIM card, and you need to enter it on the phone to unlock it.

What happened is, you or someone else with access to your phone must have maxed out on the number of tries available for entering the PIN code and now the SIM card has been blocked and can't be used. Only the PUK code can unlock it again. Both the PIN code and PUK code are listed on the SIM card pack from when the SIM is brand new.

Hope this cleared some things up about your problem. Go and find that SIM card pack for the PUK and PIN codes, then let us know if you need any more help!