This office is a very small docters office need to convert exixting network to VOIP network

Requirements:

1. need 1 main office phone number

2. need 2 rollover lines

3. need 1 fax line

4. need to connect with high speed internet

already have 1- fax server in network and 1 electonic medical record server.

it a small network. HOw do I implement it ? is vonage line for IP phone service good. any suggestion appriciated !!!! just need openion