OK, the reason you’re being charged double is you’re using both Express Transit and Tap-To-Pay. If you use Express Transit your iPhone does not need to be unlocked and just needs to be near the transaction terminal. It does not touch the terminal. You’ll need to decide which method you prefer to use.
Your issuing bank has the key to decrypt the data. The bank does not share the key with Apple. Apple will not be able to provide the account number encrypted by the bank.
The merchant is in violation of the terms and conditions of the Payment Network Operator (Visa, Mastercard, American Express etc.), issuing bank and Apple Pay usage. I’d approach the bank and ask them to work with the PNO to enforce the terms and conditions for refunds that the merchant agreed to. The last 4 digits are all that is required for a refund.
Federal law does not require merchants to have the full credit card number for a refund; only the last 4 digits are required, as stipulated for safety and security under federal banking regulations and industry guidelines. Federal law governs credit card information security and privacy, and regulations like FACTA (Fair and Accurate Credit Transactions Act) strictly protect cardholder data. The truncation requirement is industry-standard and enforced to combat identity theft and fraud. Merchants must ensure refunds go to the correct account, and they must use only the last 4 digits for this purpose.