BB Curve :: Lock Keypad Of 9360?

My phone keeps emailing and calling random people from my contacts, because I am carrying it in my back pocket. The phone is very easily unlocked accidentally as the unlock button sits on top of it, sticking out of the holster. I have even tried placing it upward down into the holster but it still easily unlocks through the holster.

What is the most efficient way to keep the the device locked for back pocket storage? I could set up a password, but as the number of bad password inputs is obviously limited, I also do not want to have accidental password input.

Is there a way to deactivate the unlock button on top and use a key combination instead? Or anything else?