How to request a refund for an unwanted subscription?

I installed an app that had a trial period. I wanted to try it out, to see if the application would suit my needs. I realized that it doesn't suit me at the moment. I wanted to cancel the subscription, but I saw that this morning they already took the money from my bank account. I paid for the whole year without being informed beforehand that the money would be taken from my account. I am not in a position to have that expense this month. is there a possibility to refinance my money?

[Re-Titled by Moderator]