UNWANTED CHARGE FOR ICLOUD STORAGE

So last July I made sure to cancel my icloud storage subscription since I was buying the google drive subscription instead. I downfradwd through my old iphone in the subscriptions setting. I made sure a lot of times that there was nothing left aside from the google drive. Also since I was selling my iphone, I reset it to factory setting. Now I received an email that apple charged me for icloud storage. When i wanted to "report the problem" it wasnt in my account purchase history but clearly I received and email and a receipt of my billing. Please help how can i get a refund and make sure this doesnt happen again?