We’ve discovered multiple methods to bypass those troublesome phone conversations, allowing you to simply leave a voicemail and carry on with your day.
Besides creating an audio file in the right format (Adaptive Multi-Rate), you also need to trick the iPhone to upload your new greeting to the AT&T servers:

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Just NowVisual Voicemail Visual Voice allows you to access your voicemail mailbox using the display menu of your phone rather than following spoken mailbox prompts. Press the Message button to use the Visual Mail Option. ***Note*** If you read your voicemail in your email it does not automatically mark it read in your voice inbox.