Barclaycard - a playground for fraudsters

I am quite a tech-savvy person and I know how to spot fraud, and how to protect myself from losing money to fraudsters. To my surprise, I recently discovered 3 unauthorised transactions on one of my credit cards which is issued by Barclaycard. Because I am using this card to pay for my balance transfer and nothing else, I have been logging into the app only once a month to pay a part of it. Just last month, when was time to pay it, I noticed that the outstanding balance was higher than what I calculated that I needed to repay. I have looked into a statement and noticed that for the last months, from September to November, each time on the 8th, I have been charged for Amazon Prime £8.99. The funny thing is, that I already have Amazon Prime, for years, but I am paying it annually and not from Barclaycard. I don’t have Barclaycard added to my Amazon account. Because these transactions are not displayed on my Amazon account, I haven’t been able to sort this out with Amazon itself and need to contact Barclaycard. Before that, I raised claims about unauthorised transactions for all three transactions. As a precaution, I cancelled my Barclaycard and requested a new one with a new number as I thought that with a new number, no more new transactions would happen. Below I will show how wrong I were in that assumption.