From Audacity Wiki
|Many cell phones can be customised with the user's own ring and answer tones. This tutorial will help you to prepare suitable sound files.
Many different kinds of file formats are used in cell phones, some of which cannot be created by Audacity. You need to research what file format(s) your phone accepts, and how to upload it to the phone, before you start to prepare the sound file. See our advice below, and always consult your phone manual if in doubt.