In our society it is very difficult (though not entirely impossible) to survive without money. If you are not in a position to withhold your labour, because you have no money, then you have no bargaining power when determining your wages. In this case, a prospective employer can essentially offer you any wage they like - will that be a truly "voluntary" contract, even though you have no choice other than to accept it?

Simplistic solutions like "just move elsewhere" ignore both the inherent difficulties that moving poses when you are living in poverty, and the situations encountered by many people who take that option. As a new arrival you face the prospect of high initial costs trying to find a place to live and trying to find work, on top of the living costs you would have faced anyway, coupled to the fact that you are likely to have a reduced support network to help you deal with any problems you might face, and help you get on your feet. This is all after the initial expense of actually moving.

You asked your parent for a proposed solution, mine is simply for Amazon to more equitably distribute revenue within the company, to spend more on low-level wages, less on high-level wages, and less on other projects if there is a shortfall. In general I suspect that some kind of employee ownership goes quite far to alleviating many problems of this nature.

As a footnote, the only sense in which a market exchange is voluntary is that all parties agreed to it, which follows from the definition, and is therefore useless: "market exchange" will suffice. It is simply a disingenuous attempt to make the idea of a market exchange sound more humane, and to suggest an absence of coercion, without ever providing evidence that this is the case.