[header] How to disguise your voice [title] Download a voice-changer app. [step] There are a variety of smart phone apps for iphones and androids that you can use to change the sound of your voice, many of them free. New apps are always coming out, so check out the app store to find out what's available. 
[substeps] Some of them allow you to record your voice and play it back in manipulated form, while others allow you to speak into the phone and project weird robot noises and other big changes. One app, call voice changer, even lets you make calls with your new fake voice.