Before the digital era, he says more than 80 percent of business lines had voice mail. Now, he estimates only a third of office phones have it.”For customers, even the most professional voicemail greeting is impersonal, and may even harm customer experience (millennials, in particular, avoid using voicemail altogether).
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.

I could see an argument for relaxing that for mobile voicemail, on the basis that mobile phones are pretty personal and not generally shared by multiple people, but I've no idea whether that may have happened. Or, indeed, whether such policies may vary between organisations within the NHS.
Rehearse or write down your message before recording it. Remember that old saying “practice makes perfect?” It’s certainly true when it comes to creating an electronic greeting. The more you’ve rehearsed, the easier the message will be to restate. If you don’t have time to practice, writing down the greeting before recording it – and then reading it aloud from the paper – may help you stay focused on the correct wording.