A dentist is similar to a doctor. Unlike a doctor, a dentist is going to get far more non-urgent calls as patients will want to know when they can pick up various orders, as well as to book follow-up appointments. The key here is prioritizing so the dentist can respond promptly to the patients who need emergency dental work and other urgent consultations.
Make sure that you set up your voicemail. To check, dial your own phone number from your iPhone and leave yourself a message. Call your iPhone from another phone and try to leave yourself a voicemail. Go to the keypad and press and hold on the 1, or press the Call Voicemail button. This dials voicemail. Check if you have any missed messages.

I have my uncle’s recording of him singing me ‘Happy Birthday’ on my phone recorder which I’ve saved since June 2016 which apparently cannot be recorded other than via speaker phone to a recorder that makes a poor quality recording. So I seem to be unable to delete it if I want to hear it again so my message machine fills up continuously. My phone is ATT. Is there any way for me to record it to save his voice to some other media so I can replay it to hear him again?(both he and my dad,his brother passed away). Are there any home phone systems available that either record to a removeable chip, cassette, or whatever which can be saved other than an audio recording to another audio recorder which declines its quality significantly?
If someone is listening to your voicemail greeting it's only because they intend to leave you a message. Don't make them listen to 3 minutes of rambling in order to do so. Plus, you're more likely to deliver a clean, professional read if you stick to shorter greetings. If more specific information is needed, direct callers to where they can find it on your website.