I don’t want to make purchase.

Hello! Please help me. I didn’t want to make purchase on some app from App Store and and he actually charged me 339 HRK for a subscription I didn’t want. whether there is a possibility of a refund? I only used the app once for a few minutes. I didn’t want that app and that purchase.help me please yours, I have been an apple user for a long time and I think all the best about you.