Stickerly Charged Me After a Trial Subscription I Did Not Want

While entering the Sticker.ly application, I accidentally activated a trial subscription without realizing it. After the 3-day trial period ended, approximately $20 was automatically charged to my card as a subscription fee. I did not intentionally want to continue with a paid membership, and I was unaware that such a high amount would be withdrawn from my account.
I requested a refund for the charge, but my request was completely rejected. This situation has caused me serious financial hardship. I am a student, and I genuinely need this money for my daily expenses and education-related needs. Being charged this amount unexpectedly has left me feeling extremely stressed and helpless.
I kindly request a full refund of the approximately $20 subscription fee charged from my account and ask for support in resolving this issue as soon as possible. I also want the subscription to be fully canceled to prevent any future charges.