When you make a purchase, Apple Pay uses a device-specific number and a unique transaction code.
So, your card number is never stored on your device or on Apple servers, and when you pay, your card number is never shared by Apple with merchants.
When you pay with a bank card added in Apple Pay, Apple Pay doesn’t keep transaction information that could be traced back to you.
There’s no need to cancel your card(s) if you lose your phone, as card details aren’t stored there. Go to icloud.com/find, use your Apple ID account to lock your phone.
Purchases, just like all card purchases, are covered by the bank’s protection against fraud, so you can shop stress-free.