Impulse App Subscription Still Charging After Cancellation

I am writing to report that I cancelled my Impulse: brain power IQ test subscription, which I purchased through the App Store, yet the charges are still being made to my credit card. Although I cancelled the subscription some time ago, for approximately the last 3 months I have continued to see Impulse/App Store charges on my OCA Mastercard credit card in Uruguay. I no longer use the service and consider these ongoing charges to be unjustified. I request the immediate cancellation of any active subscription linked to my account and confirmation that no further charges will be made to my OCA Mastercard.