The right custom voicemail narration will welcome your corporate and business customers with a professional sound, and on-hold messages are a pleasure to listen to, set to the right voice and music. Make your brand and image stand out on the phone. No one likes to be on hold. Make that experience enjoyable for your customers and clients. I can voice custom messages, with music in the background, talking about your business or products while they wait. Reassure them that someone will be with them soon. When your business relies on calls coming in, having a professional voicemail message leaves a positive impression on customers and clients. A custom voicemail narration makes calling a cell phone feel just as legitimate as making a call to your office's front desk.
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.

Don't lose customers after hours. Here are some best practices and sample scripts for professional auto attendant and voicemail phone greetings.
You can ask your admin to change the greeting language for everyone in your organization. Your admin should see this topic for instructions: Change the default language for greetings and emails.