If you cannot reach an agreement directly with your contractual partner, you must notify Viseca in writing of any unjustified debit within 30 days of the date of the invoice (or of the card statement, in the case of a debit card), enclosing documentary evidence to this effect (e-mails, letters, details of phone calls, receipts etc.).
You can find our claim form here:
Objecting to a transaction
Complaint in connection with a lost/stolen card