How to Put Your Own Message on an iPhone
Although the default voicemail greeting on the iPhone has an automated message, you have the option to personalize your phone's settings. The voicemail feature on the iPhone allows you to create a customized voicemail greeting message, which records your voice and allows you to preview the greeting using the touchscreen commands. The custom voice message recorder on the iPhone allows up to 2 minutes of recording time for your message and is automatically used as the new default greeting once it is saved.
Click the "Phone" icon on your iPhone's home screen, then click the "Voicemail" icon in the screen's bottom-right corner.
Tap the "Greeting" tab in the "Voicemail" menu, then click the "Custom" tab.
Click the "Record" button and say your custom message. The white bar above the "Record" button will turn red to indicate the volume of your voice. Raise your voice while saying the message if the red light does not reach the halfway point on the volume bar.
Tap the "Stop" button to stop recording the message and click "Save" to keep the custom message.