Call Routing - how to

Hi, I'm trying to set up some call routing but am struggling to find the perfect option to suit our needs.

We are a small single location office with 6 users.

We are wanting incoming calls to:

- be able to dial by name to reach who they are looking for and be able to leave a voicemail.  Not to reach a live person.  

- we are on the road a lot so it's easiest for our customers to leave a voicemail.

What's the best setup to achieve this?