What is going on? It says I'm subscribed in this email, but I'm not yet

I created an account a few days ago to try out Claude and maybe subscribe at a later date, but I had this email today to say I'm now a subscriber and my plan runs out on 11th March. A check of my account tells me no money has left and the invoice is showing as $0.00. Has this happened with anyone else? I'm definitely on the Pro tier but I've not been charged at all, and I never signed up for Pro. Is this a bug or some sort of free trial I've activated accidentally?