The basic rule of thumb is that callers should hear one of two things when they first connect with your voicemail — either an apology for not being able to answer the call or a “thank you” for having called. You can do both if you prefer, but keep it short and to the point.
For example, if you are no longer accepting a particular insurance plan, the end of your voicemail greeting is a great place to convey that information. For example, here is mine: “Hello, you’ve reached the confidential voicemail of Dr. Barb LoFrisco, CounselorBarb, a licensed mental health counselor, licensed marriage and family therapist

Using the services of a professional actor with experience in phone system recordings helps ensure truly professional-sounding voicemail greetings for a business. Professional actors backed by experienced audio directors and studio-grade recording equipment can produce high-quality recordings for phone system messages such as voicemail greetings.
With all of the libraries installed and the Python code modified, our app is ready to accept calls and record voicemails. But it can’t quite do that just yet. There’s one more step: Twilio actually needs to know where on the internet the Raspberry Pi is running. Since this is a local server, that’s a bit tricky, but there’s a simple solution called Ngrok.