Most VoIP solutions will require stable and consistent internet connectivity at all your office locations where VoIP will be used. At the very least, your business phone system must have access to a business-class internet link, so discuss these needs with your company's internet service provider (ISP). This should be a dedicated link through a dedicated router if you expect your phone calls to sound as if they were coming from a business and not someone's home Skype connection. At a minimum, it's important to have a router that can create virtual LANs (VLANs) and also has the ability to encrypt your voice traffic. These days, you need end-to-end VoIP security for any call.
The auto attendant feature automatically redirects an incoming call to an extension without the need of a telephone operator, while audio conferencing lets multiple users join a single call. With ring groups, you can share the distribution of incoming calls among group members. As one of the best virtual phone service solutions, VirtualPBX provides ACD queues, an advanced version of ring groups, among its features. Given that it distributes calls to a group of users, this functionality makes managing a call center with large volumes of inbound calls much easier.

If you only check and return messages once a day or once a week, let your caller know. This will avoid multiple messages by the same caller.
In reality, that's when you can bump into voice quality problems. Your IT staff not only can't control those home routers remotely, they often won't even know their capabilities. These routers were either chosen by the employee or by the employee's ISP, so even in a midsized company, you're looking at hundreds of different makes and models. Some will have more advanced features, like QoS, some won't. Those that do may also implement QoS and similar features in different ways.