I registered for a website that helps with essay writing. It said to pay $1 to register which I did. Hours later, my credit card was charged and a person messaged me on Whatsapp with rude messages when I asked why I was charged. I had since made some contact with them on Whatsapp. I have since blocked them. They are now blackmailing me that they will message my university. I called my bank to dispute the transaction. I received something from them but it was a random case; they don't know which specific case even. I also marked that email as spam. Should I be worried?