Just to let you know, anything that would block your number from being seen on a caller ID (*72 or whatever your CO uses for number blocking) is worthless as the companies that charge to your phone line don't need the display.
You can spoof your caller ID with an OrangeBox or through a few other means, however getting it to work can be a royal bitch.
There used to be a method called "op diverting" which allowed you to con your 0 op into forward you to an 800# which would drop your number if your 0 op was using ANI2 equipment; you would then, by some operators, be asked your phone number to which you could give them any old number... Note that 1800operator no longer does this, and that 1800bellsouth no longer allows you to bill to the number you're calling from
Additionally if you're using number blocking to call a toll free # it's worthless as it passes your number reguardless of any blocking on your telephone line.