Special Offer Apple Gift Card by Email issue ( education website).

I purchasesd an iPad Air thru the Apple education website on 8/5/23.. It clearly stated “special $100 gift card” and showed that indeed $100 was subtracted from total. However my credit card was charged on the supposedly “free gift card” . I did get the gift card by email the same day, but my credit card was charged $100 (actually was posted, went through, not a pending charge)- which was a separate charge from the iPad Air I purchased. Am I missing something ? Tried calling customer support but can’t go through. Thanks in advance.