I saw the charge in my online credit card account activity and quickly realized I had no idea what this was. I did a websearch for the merchant name and found out that others had been similarly scammed when making online purchases (mine was a plane ticket on Priceline.com).
I called my credit card company, they transferred me to the Reservation Rewards/ Shopper Discount customer service, where I promptly cancelled the membership. I explained I had no idea that I had signed up for any reoccurring membership when I bought the plane ticket, and the person tried to convince me otherwise, that I must have seen and willingly signed up for it (checked a box and entered my email address).
I tried to argue but he made it seem like it was completely my fault. If this is the way this company and Priceline operate, I will never use Priceline, and recommend to friends and family to avoid using it too until Priceline drops this deceptive practice of including third parties to piggy back at the time of completing the credit card transaction. Totally unacceptable and will damage their credibility (in my humble eyes) unless they fix this.