I just downloaded an app yesterday and I accidentally agreed to the subscription which was about 100 dollars a year I cancelled it but now it says it expires next year so they billed me about $100. What do I do? Is there any way to fix this?
You didn’t say which App Store you purchased, but just go to the Apple Support app on iOS or web page - https://support.apple.com/ , select billing issues and refund.
Explain your situation and see what can be done. The sooner you ask for help, the more likely you will get a result you like.