Will I get charged for roaming if I use a different SIM card in my unlocked Motorola?

[YeahRight]

I'm planning to unlock my Motorola T Mobile phone so I can use a pre paid cell phone SIM when I'm in Mexico.

Since I wont be using the T Mobile SIM card, will I be charged from T Mobile for roaming?

[Unregistered]

You can get your Motorola phones unlocked using unlock code.. you can get such code from any vendors online like WickedUnlock.com