Same thing happened to me- found out TWO of my cards were fraudulently charged with ChatGPT Subscription for 20 USD. I have never linked my cards to chatgpt and hardly ever use these cards. I was on a free account with ChatGPT. Only ever gave my mobile number. Bank says they have no idea what has happened. Blocked both cards but am super concerned this is a bigger mess than we realise. Bank is in Singapore and it was one debit card and one credit card that were hacked.