Apple didn’t refund my subscription

Hi, I wanted to ask you why Apple refused to refund my subscription. I have written everything to them and they still refused me. I must mention that app that I have been using (PicsArt) constantly shows ads of premium subscription, and I must have accidentally clicked on it. I realized i bought it when it was too late and I have already been charged with subscription. I used it for one thing while free trial week, and never opened it while the premium period started… I think it’s really unfair, and I want to know if I can do anything?