Call your bank or card issuer and get them to do a chargeback, tell them you paid for a service which was not rendered and the company refused a refund.
Also, depending on where you live, it is likely that you have a legal right to withdraw. Many jurisdictions enforce a 14-day cooling off period where any party may unilaterally withdraw from an agreement.
Not a lawyer, just a guy who refuses to let corpos get the better of me, and will use every trick in the book to fuck with them until they break.