Request Refund - Charges After Nebula Subscription

My Nebula subscription was already cancelled, as confirmed by the email I received stating that my subscription had been successfully canceled. Despite this, on 5 August I was charged 64.21 Singapore dollars for a Nebula subscription that I did not intend to pay for. On 6 August I contacted Nebula support via email and requested a refund, explaining that my subscription was already cancelled and that this charge was not expected. So far, I have not received any response to my refund request. I kindly request that this unauthorized charge of 64.21 Singapore dollars be fully refunded to my original payment method as soon as possible and that no further charges be made to my account.