Voicemail services like Google Voice, RingCentral, and similar platforms work by recording incoming calls and storing them as audio files that can be accessed later. While specific implementations may vary, here's a general overview of how these services typically work:

Call Routing: When someone calls your phone number, the call is first routed to the voicemail service provider's infrastructure instead of directly to your device. This allows the service to handle call recording and voicemail storage.

Call Recording: The voicemail service records the incoming call and converts it into an audio file. This recording captures the caller's message and any other relevant information.

Voicemail Storage: The audio file is then stored on the voicemail service provider's servers. This allows you to access your voicemail messages at any time through various methods, such as calling a specific number or using a mobile app or web interface provided by the service.

Notifications: Depending on your settings, the voicemail service may send you notifications, such as text messages or emails, to alert you about new voicemail messages. These notifications typically include relevant details like the caller's number, timestamp, and sometimes a transcription or summary of the message.

Now, regarding the usage of data when streaming audio, it depends on how you access your voicemail messages. Here are two scenarios:

a. Listening via Phone Call: If you call a specific number provided by the voicemail service to listen to your messages, it typically works over the regular voice network, not data. In this case, you would be using your regular phone call minutes or plan.

b. Listening via App or Web Interface: If you use a mobile app or web interface provided by the voicemail service, it may utilize data to stream the audio files. When you access your voicemail messages through these methods, the audio data is transmitted over the internet, and it would consume your data plan or Wi-Fi connection.

It's worth noting that data usage for streaming audio can vary based on factors such as audio quality settings, the length of the voicemail message, and the specific implementation of the voicemail service.

In summary, voicemail services record incoming calls, store them as audio files, and provide you with various means to access and manage your voicemail messages. The data usage depends on how you access your messages, with traditional phone calls not utilizing data but app or web interfaces potentially consuming data for audio streaming.