I have a $50 USD Delta eCert that I bought to trigger a $50 statement credit from the Delta Gold Amex. The terms of the cert allow it to be used for airfare, taxes and fees but no other expenses.

I am attempting to buy an award ticked and pay the taxes (approx $52) with the certificate. When I try to use the certificate I only have the option of booking revenue tickets. If I switch the display from $ USD to miles, the eCert gets deactivated.

Is there any way around this or do I need to call Delta? Will they waive the phone booking fee in this case?