Summit Pty Ltd $($Summit$)$ is a commercial agent in Sydney whose business involves purchasing old debts at a discount and then pursuing the debtors for payment. Lucy, an unemployed mother with a disabled, dependent child, had defaulted in making repayments on a car loan of $$2,000$ with the National Finance Ltd $($National$).$ Despite the fact that National had repossessed and sold Lucy$$s car, the amount recovered by National was insufficient to discharge Lucy$$s loan debt entirely. When Summit eventually purchased Lucy$$s debt from National some ten years later, accumulated interest had increased the amount Lucy owed to $$10,000.$

An employee of Summit contacted Lucy by telephone and indicated that if a satisfactory arrangement for payment could not be reached legal proceedings would be initiated. In the course of that telephone call, the parties reached an agreement that Lucy would pay $$5,000$ as satisfaction of the debt. The amount of $$4,500$ was immediately debited from her credit card and Lucy agreed to make arrangements to extend her credit limit on that card to enable payment of the remaining $$500.$

Advise Lucy of her legal position in these circumstances. Support your answer with case law and legislation where applicable.