In order to authorise online payments securely, card data protection is required. That's exactly what Mastercard ID Check does, protecting your card by:

• confirming online payments from the BT Pay app with fingerprint, FaceID or phone unlock method. Every time you make an online payment, you instantly receive a notification on your phone and confirm the transaction using the phone's unlock method
• entering two passwords: a dynamic password, received by SMS, on the declared phone number and another unique password, defined by you when you pay online. You need to change your unique password every 90 days.