I’m actively researching phone services for our company, and I agree with some of the others. This is an overview more than a review, doesn’t go in-depth enuff. But, it’s a good start for me, I did find it helpful, weblinks are easily accessible. Just not as informative as I’d expected and hoped.
Whether you need phones for opening a new office, supporting employees working from home, or it’s time to update your business phone system, we have done all of the research and tested over 25 small business phone systems to prepare the list of our best Top 5 most recommended business telephone systems. The manufacturer must be reliable, with a proven history and warranty support. Be the most affordable for a small business to purchase and maintain. Be future proof — compatible with standard analog landline telephone service or VoIP cloud phone service. Provides feature to transfer calls to a cell phone, a smartphone app, and supports mobile and home office employees. Must have the essentials: automated attendant call tree menus, voicemail to email, intercom, call forward, transfer, and music on hold.

A Ring Groups or Hunt Groups feature lets calls ring multiple people inside a group. The GIF shown here demonstrates how calls can ring one user before ringing a different user in the same group.
This is a tough category because all telephone service companies have complaints on public forums. Remember that people who comment on these forums are more likely to be unhappy with the service, while happy people don't frequently take to publicly announcing their happiness with a product. Acknowledging that all the companies we looked at have some complaints, the winner for best service is Vonage, one of the first phone companies to offer VoIP for business.