KiltedTim thanks for your fast response.
I understand that Verizon phones are CDMA phones. And I've done the exhuastive forum searches online to understand the process (although I have seen major differences in the success rate of other who have tried to use Truphone with the Verizon iPhone 4s).
From what I've read, Verizon will allow you to use an international SIM in your phone and the process for getting your phone working with an international sim is to:
1) Call Verizon (global services) and have them unlock the SIM slot for foreign SIM cards.
2) Turn phone off and replace the Verizon SIM in the SIM tray of the iPhone 4s with your foreign SIM.
3) Turn phone on. It will tell you that "Activation is required". I can confirm that this happens when I turn the iPhone 4s on with Truphone SIM inserted.
4) Connect to phone to iTunes with a cable or "iCloud" services and allow the activation process to complete.
5) When complete the iPhone should show that you are roaming on whatever local GSM network exists. (Can't confirm this occurs, but form other forums others have been able to successfully get to this point.)
Sorry if this explanaition is overkill but I wanted to show what I meant by activation. Also this is the process that has been explain on many other forums.
So from this process I interpret the following has to happen to allow the phone to use foreign SIMs:
1) Verizon somehow notifies the apple servers that communicate with iPhone devices that device with serial number "xyz" can use foreign SIMs.
2) The user has to then allow the phone to "communicate" with the Apple server to get the updated SIM unlock settings. You do this by connecting via Wi-Fi or through iTunes (depending on whether you choose to allow the phone to activate via Wi-Fi or tethered via cable to iTunes).
And finally, I totally understand that I cannot use any US GSM carrier with Verizon iPhone (T-mobile or Sprint). And perhaps this were the problem lies. I am trying to get the iPhone to work while I'm still in the US and not already abroad. It's just funny that others have been able to connect to GSM networks with a Truphone SIM inserted while still in the US (search for this article on ZDNet: International Travelers: Here is how to SIM unlock your Verizon Apple iPhone 4s). I guess I'm under the assumption that a Truphone is an international roaming provider.