To Cancel My ShortMax Subscription

I had a subscription with Shortmax Innovation, which I cancelled through their website on 19 March. Despite this, since that date, Shortmax Innovation has continued to attempt to charge my Sterling Bank card every time the subscription is due. None of these payment attempts have been successful because I make sure there is never enough money in the account, but the repeated charge attempts are disturbing and worrying, and I do not want any future risk of a successful debit. I contacted Sterling Bank, and they informed me to keep trying to reach Shortmax Innovation, but this has not resolved the issue, and the attempts continue. Through this complaint, I request that Shortmax Innovation immediately and permanently stop all current and future charge attempts on my Sterling Bank card and fully confirm that my subscription is cancelled in their system so that no further billing will occur.