Charging For Unknown Subscription

I recently discovered that a company called Sweetmax has been repeatedly attempting to charge my debit card. Fortunately, these transactions have been declined because I do not have sufficient funds in the account, but I am very concerned that these attempts are being made at all. I first noticed these declined Sweetmax transactions today when I checked my bank transaction history. I do not recall ever subscribing to any service or entering into any agreement with Sweetmax, and I have never knowingly authorised them to bill my card. I request that all current and future charging attempts by Sweetmax on my card be stopped immediately. I also ask for a clear explanation of why these charges are being attempted in the first place and under what alleged subscription or agreement my card details are being used. I expect a prompt investigation and a written response clarifying the situation.