refunds for subscription

hello, I have a subscription in the application "where are my children". In the app, I deleted the account and then deleted the app itself. Due to the fact that I am using the iPhone recently, I did not know that the subscription needs to be canceled separately. I was charged today for using this application. technical support replied that they could not refund the money, since they did not have access to Apple's payment system and advised you to write to you to cancel the subscription payment. can you help me?