Is the device locked to the TMo network? Is their an account still tied to the PIN? As far as I know TMo locks their BB to their network, that being said if your in good standings with TMo (have been a cust. for over a yr. bills are paid etc.) they should provide an unlock code to unlock the 7100 to work on other networks. If that doesn't work you'll need a third party service to unlock the unit for you or take a look at the follwing:
http://www.bongowireless.com/pages.php?pageid=16#11 their in the Toronto which could be of use to the cust. whom bought the 7100 from you as they could unlock the 7100 for the Rogers network.