ShortMax Refund - Continued Attempt To Charge After Cancellation

I had a weekly ShortMax subscription purchased through the Apple App Store in the UK under my Apple ID, starting with rm and ending with @icloud.com. On 23 April, I requested to cancel this subscription and received a written email confirmation from ShortMax stating that my subscription had been cancelled. Despite this confirmation, I have still been charged for the same subscription on 1 May and again on 8 May, for a total of £29.63 GBP. These charges were taken after the confirmed cancellation, and I no longer wish to use this app or have any association with this subscription. I request that the full amount of £29.63 GBP be refunded and that my ShortMax subscription be completely and permanently cancelled so that no further charges are taken from my account. I would also like written confirmation that the subscription has been fully terminated.