I use Google Voice for my Signing Business. With Google Voice I know when to answer the phone with "Hello" and when to answer professionally. Here is how to set it up:
Go to Google.com. If you have an account with Google sign in if not set up an account.
Then in the top right corner you will see a bunch of dots. Click on them. At the bottom of the pop up box is a link to more. On the new pop up box at the bottom click on even more. On this page drag down. In the left column about half way down you will see Voice. Click on it. You want a new phone number. Follow the prompts. Once it is set up click on setting wheel. Click on the Calls tab. Next to Caller ID (incoming) mark Display my Google Voice number.
Now go to your cell phone and save your new number as Signings. This way when your phone rings you will know it is a Signing Company calling.
When ever you sign up with a company use your google voice number so that when they call you will know how to answer your phone.