123SPOOF Mobile is a Blackberry application that gives you control over your phone calls, allowing you to change caller ID, disguise your voice, record your calls, and more.
Another great feature is the ability to make free calls with their ad supported service. Before every call an ad is played but at least your call is free right? I would do this for a lot of things in life. For example, give me a free beer in exchange for forcing me to wear headphones that play ads while I drink. No problem.
The app is free and you can download it here. (FROM DEVICE)
There is a premium paid service too. More details here.