I paid for Delta Economy Comfort seats on April 2 for 4 legs. Each seat showed as a separate charges on my AmEx plat credit card, posting on April 3. On April 4 the credits showed up on my account.
Sometimes AmEx doesn't recognize the charges right away and I know others have had to call and get the credits. Though I have not ever had to call.
Hope this helps. You may just need to call if it has been more than a few days.