If that doesn’t work, you may need to either live with the voicemail notification just sitting there, or you may need to try a full reset of your iPhone. It is a step of last resort but can fix most problems with iOS so maybe worth a try. Just remember to back up your phone if you decide to give it a try.
Are you creating a voicemail greeting for your entire company or team? These business voicemail greetings will do the trick.

With this method, you don’t need a third-party app. Call the person you want to chat with, then tap the “Add Call” button on your phone’s screen. Dial your own phone number—the one you’re calling from. This will take you to your voicemail. Once your voicemail has started recording, tap the “Merge Calls” button on your screen. Now, you’ll record your phone conversation onto a voicemail message. When you’re done with the call, you can tap the share button to export it to your Mac via Airdrop, to the Voice Memos app, or transfer it via email or text message. The file is recorded as an M4A, so depending on what you want to do with it, you may need to convert it to MP3 before uploading it to other apps.
For small businesses, there are a variety of voicemail service providers you can use that offer different features. From transcription and voice to text to more convenient features of handling multiple phones through one number, availability varies by service. Shared voicemail and call routing is intended for multiple access and directing calls to one or multiple phones. Mobile apps are also available that allow you to check your messages from your phone. The below infographic outlines the current state and trends of voicemails.