If you want them to leave a voicemail, tell them right from the beginning, “Please leave your name, reason your calling, and the best way to contact you.” If you want them to call you back during normal business hours, tell them, “Please call back during normal business hours.” If you want them to call back prepared for a lengthy conversation, you can say something like, “Please refer to our website’s FAQ page,” and then provide the URL. Self-service should never be underestimated.
Website: https://www.openphone.co/blog/21-professional-voicemail-greeting-examples/

The best voicemail message isn’t as good as you picking up the phone. A key to client service is being available for clients. If you find you need some help with this, you might think about hiring an assistant , how you can deal with having too much work , and how you can change your behaviors to be more productive.
Of course, we want to know as soon as an incoming voicemail is saved, so again, it’s Twilio to the rescue. By adding a few lines of code to our Python script, Stacey and I each get an SMS notification telling us there’s a new message. Note that Twilio’s API requires a separate call for each message to be sent, which is why the similar code repeats once for Stacey’s phone number and then again for mine. If you plan to send bulk messages from Twilio, I expect that you can build a list of phone numbers and loop through them with the API call. Since we only have two contact numbers and don’t expect to add any more, I decided not to loop through a list of two elements.