My Apple trade-in refund sent to wrong credit card number

Apple approved a trade-in refund on my old iPad and indicated that refund was being issued "to your original payment method" (a VISA card). However, the VISA card number on the "good news, your refund is complete" email shows the last four digits of a credit card number--but the fourth digit is wrong and does not match the last digit of the VISA card that was charged for the cost of my new iPad. Who do I contact to straighten this out?

[Re-Titled by Moderator]