PDFSmart - Complaint & Refund

I am writing regarding several unauthorized charges that PDFSmart has taken from my NatWest card ending 0832, while I am using the service in the UK. On 10 February, I was charged 49.99 GBP on the PDFSmart website as an auto-renewal of a subscription that I did not knowingly authorize or consent to. As soon as I noticed this unexpected charge, I contacted PDFSmart support and requested that the subscription be cancelled. Despite this, on 6 May, I was charged 49.99 GBP three separate times, again without my consent and without any valid reason, even though I had already asked for the subscription to be cancelled in February. After seeing these new charges, I contacted PDFSmart customer service, but I have not received any response so far. I request a full refund of all 49.99 GBP charges that have been taken without my clear consent, and I also want the subscription to be fully cancelled so that no further payments are taken from my card.