A few years ago I wanted to have a separate phone number for a startup company, but since we are only a few members, and in different locations, it needed to on a system we could all make calls from it and redirect for availability. After trying a couple I've found RingCentral.com to be the best and most affordable.
Here are some of the key features for a small company that can make you look like a big well run operation. First you choose a number for your business, then with their phone app, you to make and receive calls from your cell phone with the other number. When some calls your business you can route them by extensions you set up to other employees cell phones and everyone can make make and receive calls from that number. It's one of many great features, plus you have logging to see what calls have been made. This feature is really helpful to make sure you don't miss or followed up on a call. There's even a feature for direct digital recording your calls.
Take a test drive on RingCentral.com.