The rules/restrictions for the fare bucket of the ticket you purchased are relevant. Depending on what sub class you bought, you might be able to refund your ticket with a small (or even no) charge. It depends on the terms. More info on your ticket would be helpful.

What most likely happened is that your ticket sub fareclass price (Y/B/H/K/L/M/ whatever) didn't change at all. Rather, they may have released additional seats for a lower fare bucket than yours that previously didn't have inventory when you were buying.