To use a different greeting you already recorded or switch back to the default greeting: On your Android device, open the Voice app . At the top left, tap Menu Settings. In the Voicemail section, tap Voicemail greeting. Next to the greeting you want to use, tap More Set as active.
You might also consider giving them the option to skip your voicemail message completely by pressing another key (again, check with IT). You also want to make callers aware what you will return their call, instead of telling them that you will try to return their call--and let them know when you are likely to do it, if possible. If necessary, provide additional or emergency information in your voicemail greetings. My dentist, for example, lists his cell phone number for emergencies.

I can't get to the phone before it goes to voicemail. I understand that the number of rings the caller hears is controlled by my carrier, Verizon. My husband has a Samsung Galaxy S7 purchased from Verizon and when he calls, he hears 8 rings then it goes to VM. Note that I called Verizon and they set it to 8 rings, the maximum available.
30. Hello, you’ve reached [your name]. I’m currently out of the office and will return on [X date]. If your call requires urgent attention, please call [Name] at [phone number] and they’ll be happy to assist you. If not, leave a message and I’ll return your call when I get back.