As mentioned above, alerting callers that they won’t be getting an immediate call back is of upmost importance for an entity’s reputation and a caller’s satisfaction.
If your customers feel that you don’t care, they’ll take their business elsewhere. Experiences are the differentiating factor between businesses. Big efforts to improve the overall experience in tiny ways by crafting a voicemail greeting script can make a huge difference when customers are asked by their friends and family how easy it was to work with you. And word spreads quickly in the age of social media. The more positive experiences you offer, even when you’re not available, the more likely those people will call back.

Last, you'll want to take a close look at your current network monitoring tools. At its core, VoIP is simply a specific kind of network traffic, so in the end it'll be these tools that allow you to see that traffic and manage it across your network. Make sure that the tools you're using support VoIP's needs, especially around QoS, traffic analysis, and network congestion issues.
When you’re looking for a job, a good rule of thumb is to answer your phone as often as you can. You never know when a recruiter might be calling to set up an in-person meeting, or conduct a phone interview.