If you persistently can’t save your greeting, you may need to reset your phone’s network settings. The iPhone needs to access your network’s data connection to save changes to your voice mail configuration, and if it can’t connect to 3G or 4G, it won’t save the changes.
When was the last time you checked your voicemail for missed messages and paid attention to your greeting? If you’ve activated your Voice over Internet Protocol (VoIP) phone’s voicemail transcription feature for convenience, chances are it’s been ages since you last listened to your voicemail greeting. So it's probably time that you took the time to update it for your callers.

It’s a good practice for each of your team members to have their own personal business phone numbers. There are many reasons why they shouldn’t use their personal cell phone number for business, so you’ll want to give them their own phone number through your VoIP provider or phone system.
Customers do not possess the expertise and knowledge you do. When creating your business voicemail greetings, make sure you don’t use such technical terms that the customer may not be able to understand.