I burned through the $300 annual Marriott statement credit in my first month with the Marriott Brilliant card. My Marriott spend that month on the card was at least $400. Now a hotel is returning $30 of the credit to me, due to an overcharge.

Q: will Amex automatically apply that $30 to remaining prior Marriott spend on the card, issuing a new credit in that amount? If not, will Customer Service do it manually? Or do I have to incur new Marriott spend to make us of the $30?

Thanks...