Your customers might need you on the holidays. If you’re a business owner, you know this already. 🙂 Manage customer expectations and let them know how to get assistance.
If a phone rings once and then goes to voicemail or rings only briefly, it You can't definitively know the cause of a phone barely ringing and going to voicemail because neither a phone company nor the phone's operating system provider will tell you if your phone number is blocked.

Another alternative for Android users who don’t have the option for ‘Route to Voicemail’ in their settings can use the Do Not Disturb function. Although this prevents anyone from calling, you can add exceptions.
When you first set up your Android phone, it may ask you to record your greeting for the caller. You can also keep the default greeting stored on the device. But, in future, if you want to customize the Voicemail greeting or want to create a new one, then you may need to delete the old recordings from Android. It may not be necessary depending on the Android device model & version; it’s good to know the process.