academia.edu review: Return $249.00 to my american express card

My credit card was charge $249.00 without my knowledge. Why was I charged? I no longer want the service because I no longer need it. I received 4 emails in Dec. saying I could get the Premium Service for $1. I did not respond because I don't need it. And then I find out from my credit card company that I was charged for it. But looking on my account, it says I don't have Premium service. My American Express credit card was charged on December 25th without any email telling me it would be charged. It needs be reimbursed, please.