Sometimes, when the phone is not picked, the caller is automatically redirected to the voice mail. That means that when someone calls you, he or she will hear some dial tones before going to the voice mail where they could record their message. In Verizon, you can actually set the number of rings before voicemail.
This iOS app does basically the same thing as the above method. It starts a call, initiates a second call, then merges the two so it can be recorded. However, instead of calls being stored in your voicemail, they’re stored in the app. Automatic Call Recorder Pro costs $4.99.

2. Voice Training: 30 days to a more confident powerful voice (Udemy) Are you someone who has a lot to share with the outside world but are reserved because somehow you feel your voice doesn’t carry enough authority?
To improve a a business voicemail greeting, keep these eight rules at the forefront of the creative process: Avoid turning customers off with overused and impersonal phrases like “your call is very important to us..." Avoid leaving customers unsure by not immediately telling them the business, department, and/or person they’ve reached. Avoid leaving customers confused with too many details and complications; just keep it simple. Avoid messages longer than 25 seconds. Do apologize for being unavailable at the moment. Do invite the caller to leave a message. Do tell the caller when they can expect a return call and actually follow through within that timeframe. Do tell the caller about any applicable alternative options of contact and information- website, live chat, email, social media, or emergency numbers. Voicemail Greetings 101