There is an all-in-one app for both changing one's voice and spoofing one's caller ID for JB iPhones (
link ). Or one could download the free voice changer app for the iPhone (
link ). Then, simply sign up for a throw away google voice acct, pick an LI exchange, install google voice on their phone, and call from there, while using the free iPhone voice changer. All for the cost of USD$0
Even so, voice altering software/equipment, can only take a person so far. That is, it alters the tone, pitch, and can even add distortion. It however is unable to mask unique annunciations and pronunciations, or the metre, for that matter. In other words, people's vocal signatures are unique and tough to truly mask.