If you want to make it easy for your customers to contact you regardless of where they are in the country, consider an Inbound Number.
What are the benefits of an inbound number and which should I choose - 13, 1300 or 1800?
An Inbound Number is a virtual number that is linked to one or several real numbers and are either free to the caller (1800) or a unit fee to the caller (13/1300).
If you have multiple sites around the country you can set up call collection areas, usually state-based but they can also be post-code based, that send calls to different numbers depending on where the call comes from. Calls from mobiles can be set to go to different answering points to calls from landlines. Since calls from mobiles generally cost more you may want to prioritise those in your phone system to minimise the operating cost. Answering points can also be changed based on time of day and day of week. If you use a virtual assistant then calls can easily be overflowed to them.
The choices of number are:
A 10 digit number with a 1800 prefix (aka "Freecall") which, as the name suggests, is free to the caller if they are using a landline. Call charges are still applicable if calling from a mobile. The owner of the number pays for the call at a rate that depends on where the call comes from, local, national or mobile. It also depends on whether the answering point is a fixed line or a mobile.
A 10 digit number with a 1300 prefix is a fixed cost to the caller similar to a local call charge. Different charges apply when calling from a mobile. The owner of the number pays for the call at a rate that depends on where the call comes from, local, national or mobile. It also depends on whether the answering point is a fixed line or a mobile.
There is also a six digit number with a 13 prefix. Due to the very high rental on these numbers they are generally only used by big business who expect lots of calls and want to provide the shortest possible numbers to their customers. There is also a six digit number with 18 prefix but these are very seldom seen.
If you want a specific Inbound Number then this may be able to be purchased from the Australian Communications and Media Authority (ACMA) and then hosted with any carrier you choose. Alternately, if you just want a number then you can pick one from those available from a carrier.