Thank you for calling the office of (office or department name) at Eastern Oregon University. We are currently working remotely in response to the coronavirus outbreak, and may not be able to check missed calls regularly. Please contact us at (department email) or leave a voice message. In case of an emergency please contact Campus Security at 541-962-3911. Thank you.
We managed to discover some of the most common causes that will trigger this particular issue. We have done this by looking at various user reports and the repair strategies that they used to get the issue resolved. Here is a shortlist with common scenarios that have the chance of triggering this particular error message:

Note: If necessary, delete an existing greeting (limit of 2 greetings) to make room for the new greeting: Tap the Menu key, tap Delete greetings, tap the check box next to the desired greeting, and then tap Delete. Tap the Record icon to record your greeting. Tap the Stop recording icon to stop recording. Start by tapping on the phone icon found at your iPhone’s home screen. Go to the setting section on your iPhone. Now, you can go to the keypad on your phone and then type the number #404 and then call so that you are able to turn off voicemail on iPhone. How do you delete your voicemail greeting on iPhone? Tap Voicemail, then tap a message. Do any of the following: Play the message: Tap . Messages are saved until you delete them or your carrier erases them. Share the message: Tap . Delete the message: Tap . Why can’t I change my greeting on my iPhone?
So make sure you connect with them to make sure you have it. If you don't see that play on the record and that way you'll just have to basically record and use a different device to call them yourself, to hear your voicemail. I hope you found this useful. Please give it a thumbs up and subscribe to this channel for easy-to-follow, how-to videos, and tech videos, just like this one and I'll catch you next time. Thanks for watching.