Your iPhone can now send spam calls directly to voicemail — here's how to set it up. But, if your iPhone thinks it knows the number — like if you've called someone who isn't in your phone In one instance, for example, I had this turned on and my colleague's calls kept going right to my voicemail.
Click on Audio Library Click Add Audio Speak into your mic to get level then click Next

To enable Visual Voicemail, you must create a password by accessing your voicemail and then record a greeting as follows: Access the Telephone app, select the Voicemail tab and tap Configure now. Select a password for your voicemail and tap Done. Confirm your password by re-entering it and tap Done. Select Custom if you wish to save a new greeting or Default if you don’t wish to edit your message. Tap Save.
This article is about the second main type of greeting – the voicemail greeting. All businesses should have professional voicemail greetings at the company level (i.e. your general business number), department level (e.g. customer service), and employee level, where applicable. It’s important that each of these voicemail greetings align with the brand and personality of your company to ensure that every caller has a consistent experience. Let’s dive in!