Amazon Prime: how did I become an ‘accidental’ member?

I ordered one book but my account was debited with £7.99 in each of the subsequent four monthsI bought a £7.99 book from Amazon and later noticed that my account had been debited with £7.99 in each of the subsequent four months. I assumed this was an error and placed a block on future payments, but have so far been unable to find a way of securing a refund. SL, Banstead, SurreyIt looks as though you are one of the many who inadvertently signed up to Amazon Prime, a £79-a-