Hello, you have reached the dental office of Dr. X. We are busy assisting a patient now, but will call you back as soon as possible. Please leave your name, reason for calling, and your number. If this is an urgent enquiry, please call 911. In this case, the dentist is giving a reason for not being available and they’re providing a way to prioritize the patients who need the most help. They’re also leaving an emergency number for the most severe of situations.
iPhone users have another option: You can send a voice message from Apple's Messages by tapping the microphone button inside the text box (this works only when you're messaging other iPhones). By default, these voice messages last for only two minutes before they are deleted, but you can change that. Either tap Keep under any sent voice message or go to Settings > Messages and tap Expire under Audio Messages. You can set the expiration date to Never, but this affects only your record of the conversation, not the recipient's.

Hi, we aren’t in at the moment, if you are trying to sell us something please start speaking now and hang up at the beep, everyone else start speaking at the beep and hang up when you’ve finished.
Whether it’s an out-of-stock product, a canceled event, or social media snafu, there are times when your business may see an influx of frustrated callers. While it is important to address their concerns head-on, you may not be able to answer each call as it’s received. Make sure you use best practices for dealing with angry customers, and that your voicemail greeting sets the appropriate tone. Avoid defensive language, validate their concerns, and keep them informed as to how you are handling the situation.