Write the next sentence in this paragraph:

How to sell or swap gift cards
Use a gift card market site.
There are sites online that allow you to swap and sell gift cards, known as gift card marketplaces. These sites offer a balance guarantee on any card purchased or sold through them.
This ensures you are not scammed or given an unfair price for the gift card. They work as the middleman between buyers and sellers so you only deal with the company and not with any third parties.