Why am I not eligible for a refund after canceling an app's subscription?

I first bought a 3-day free subscription to use this app and then after this i canceled the subscription and never used this app again weeks later I get my allowance for chores i did for a month and when i look back at my money after a few minutes 30$ is gone so i request a refund and it says im not eligible for one i don’t think this is a good way of running things i basically just got robbed I would like my 30$ back

[Re-Titled by Moderator]