Hi Anastasia,
First step any lawyer would take on your behalf if you retained one would be to send a letter of demand, but you can do this easily yourself.
Here is one you can use to DIY:
Letter of Demand Template for Australia - Legal Documents - LawAnswers.com.au You just need to include all the necessary details so that the creditor can assess see why the money is payable, and the total sum and how it is calculated. If you provided a quote for the work or you have sent an invoice then you would attach this to the letter as well. Make sure you state something to the effect of, "Should $x amount not be paid by [X date] we reserve the right to refer the matter to our solicitors to take legal action."
If you get no love from the first demand, send a second entitled "Letter of demand - final notice" or something to that effect. State at the end of that one that if the money is not paid you will be instituting legal proceedings. If you don't receive payment of the debt by then, you can then explore your options to institute proceedings. Depending on how much you are claiming it may fall within the small claims division or Magistrate's Court. You will need to file a Claim and go through the litigation procedure.
