PDFSmart Misleading Subscription Model

I used the PDF Smart service for what was clearly presented as a one-off payment of £1 for a single document conversion. I made this £1 payment on 22 February using my NatWest card and did not use the service again afterwards. Despite this, on 1 March an additional £49.99 was taken from my NatWest account without my knowledge or consent, and I only became aware of it when I saw the transaction on my bank statement. I feel misled, as I believed I was making a single one-time payment and at no point did I knowingly agree to an ongoing or higher charge. After noticing the £49.99 payment, I contacted PDF Smart support from my email address [email protected] and requested a refund, but I have not yet received any response. I have proof of the transaction from my bank and can provide it if needed. I kindly request a full refund of the £49.99 that was taken from my account and confirmation that any subscription or recurring payment linked to my details is cancelled so that no further amounts will be charged.