eDreams Charged £99 for Prime Without My Consent

I recently discovered that eDreams had taken £99 from my account for an eDreams Prime subscription that I never knowingly subscribed to or authorised. The payment was taken in August via my Zilch card, which is linked to my Ulster Bank account. I did not agree to this Prime membership, and I was not aware that such a charge would be made. After noticing the £99 payment, I contacted eDreams customer service to explain that I had not subscribed to Prime and to request a refund. I was informed that they had received the cancellation but that no refund would be given. I find this unacceptable, as I never knowingly consented to this subscription in the first place. There may also be other amounts taken that I might not have noticed yet. I am requesting a full refund of the £99 Prime charge and a review of my account to identify any other similar charges that I may have missed, with a refund of those as well. I also ask that any Prime or similar subscriptions linked to my account be fully cancelled so that no further payments are taken without my explicit consent.