A virtual credit card, as a set of data, free of a physical substrate, the data being adapted to authorize a person who is in possession thereof to pay for a product or service, in particular in the framework of an online transaction, the data set being produced on the basis of a credit card account or a pre-payment and in response to a user authentication procedure involving an evaluation of biometric features of a user, in particular of his/her voice profile, and being available at a telecommunication terminal, in particular a mobile phone, of the authenticated user.