There is no way to get your card account number from your device or by using Apple Pay. Your device does not even store your Account Number.
One thing that can happen is that your card info was skimmed from a retail terminal. Scammers commonly install these at Gas Stations and ATM's where there is little interruption overnight. Once someone has your account number, they can add it to a device if your bank approves it. Apple does not approve/deny cards being added to the Wallet since they have no information about the account holder of the card being added, which is why the bank has to approve the card with the device and account information that Apple sends to the bank. After the bank approves the card, then they send a unique token to that device, so it can be added to the Wallet and it is that token that is used for purchases, not your account number.
Follow up with your bank, as they would know if the charges are coming from your device or if they had mistakenly approved your card being added to another device. If the charge came from your device, that can only happen after authorization with FaceID/TouchID or Passcode.