The problem there is that VoIP traffic is much more sensitive to network bumps and potholes than most general office traffic. That translates to conversations breaking up or cutting out entirely, difficulty connecting over Wi-Fi, or (worst case) dropped and lost calls. If your business is small and your network is essentially contained in one or two wireless routers, then your configuration and testing headaches might be fairly small (though still there). But for medium and larger networks, these tasks can not only be complex, but also time consuming, which translates into added cost in terms of man-hours.
While home VoIP systems are fairly straightforward to set up and use, a VoIP system for all but the smallest of businesses can be quite complex, In addition to have multiple users, business VoIP systems have complex feature sets that are necessary to conduct business in today's world. In addition, a business VoIP implementation must take into account the existence of the data network, even though in most cases it won't share the same infrastructure. This will mean switches and routers optimized for voice traffic, and security that's suitable for both business and VoIP.
An IP phone or VoIP Adapter (ATA) – You’ll see a wide range of prices between the different providers when it comes to equipment. Some providers have expensive equipment and “freemium” service; others will lease you equipment for free and charge more per month. Between those two, you have a lot of in-between. An IP phone plugs directly into your modem or router, and an ATA lets you use a legacy phone over the VoIP network. You need an IP phone to truly enjoy all the benefits of VoIP calling, which is why VoIP phones are becoming more popular.
The only additional piece of equipment that you need is an Analog Telephone Adapter (also referred to as an ATA) that allows you to connect your existing telephone to your home Internet. This equipment is typically provided on a free lease basis from the home VoIP provider that you choose, or you can use you own device if you prefer. You can also use IP phone(s) instead of using the ATA with your existing analog phones. The sound quality is better but there is more up front cost as IP phones are more expensive than the ATA devices.