Thanks for the info. As for the scam or whatever it can be called, I was referring to all the unsuspecting customers who turn on their phone only for a minute to check someting while overseas and then turn it back off, yet from that point forward they accrue roaming charges for anyone attempting to contact them. From their standpoint the phone is OFF. This part is NOT disclosed by TMO, nor is the fact that they disable the option to allow the customer to turn off call forwarding completely from the device.
When I attempted to turn off call forwarding (conditional or unconditional) by selecting "DO NOT FORWARD" from the call settings on the 8100, it appears to accepts the command. From this point forward all I can assume is that it will NOT forward any calls. However, if I check the call settings again, it defaults back to forwarding all calls to VM. This is NOT disclosed by TMO.
Regardless, it appears the best and only ways to avoid this problem is to either call CS and disable VM, or set the phone to unconditionally forward ALL calls to VM before leaving the country. Hopefully this will do the trick.