“Hello! You’ve reached the voicemail of [your name], [your job title]. I’m currently either away from my desk or on the other line. Please leave your name, telephone number, and a short message after the beep, and I’ll be sure to get back to you as soon as I’m available.” Press and hold the 1 key to access the voicemail system. When you hear the recorded message, press the # key to bring you to the system menu. Press 4, for the Personal Options followed by 2 for Personal Greeting. Follow the prompts to record, listen to, re-record and save your greeting. How do I change my voicemail number on Samsung Galaxy s8? Find “Voicemail number” Press Phone. Press the menu icon. Press Settings. Press Voicemail settings. Press Voicemail number. Save voicemail number. Key in +61414121121 and press OK. +61414121121. Return to the home screen. Press the Home key to return to the home screen. Dial voicemail: Press and then hold on the envelope icon displayed on the main screen. Enter Your Accounts Password: Enter the password if prompted. Delete voicemail: Tap 7 on any voicemail and it will be deleted successfully. Open the dial pad on the device. Open the application drawer and scroll through to find the Phone app. Dial Voicemail. Tapping the number 1 and then hitting the green phone icon at the bottom should call Voicemail. Enter a password (if there is one). Skip through messages. Delete a voicemail. Log into Google Voice. Click on the gear icon. Select “Settings” from the menu options. Click the “Voicemail & Text” button. Click “Record New Greeting” in the Voicemail Greeting section. Enter the name for the greeting you are going to record. Select forwarding phones. Click “Connect.”
Note: The uploaded file should meet the audio file requirements. Record a voicemail greeting from a phone: Place a call from system, the extension users can answer the call and record their voice as voicemail greetings. Record or upload voicemail greetings for extension voicemail

On the iPhone, go into voicemail and tap "Greeting". Record a few seconds of something and tap stop. Before you tap save, use iFuntastic or SFTP to navigate to /var/root/Library/Voicemail on your iPhone. You'll see a file called "Greeting. amr". This is the audio you just recorded. Delete that file and replace it with your custom message which should then be renamed to "Greeting.amr". Tap "Play" on the iPhone to verify your message works. If it plays, tap "Save" and your custom message will be uploaded to AT&T's servers.
If the you haven't changed your personal greeting, a default system greeting will be played for callers. For example, "Please leave a message for John Smith. After the tone, please record your message. When you finish recording hang-up or press the pound key for more options."