Help with Design of system

I am a Dentist looking for a way to integrate 3 branch offices (geographically separate) to 1 center to take all incoming calls to book appointments. All locations are currently connected by VPN. Besides this I also want to be able to direct all outgoing using a VOIP supplier for all landline calls and direct all outbound mobile calls via gsm dialer.
I am a newbie and am hoping to be implement a solution as soon as possible.
Bye the way I am in Australia and is there freepbx users in Australia
Many thanks