what did you tell them to get it?
I told them that I added the gift cards to my cart and entered the promo code but it didn't change the total.
They asked where the promotion is so I gave them the link.
They told me to place the order and it should automatically apply the gift card afterwards (I don't think the promo was properly set up, and I don't think the reps actually understand the promo)
I placed the order and told them that nothing happened, I didn't get the extra $25, so the rep said as a one off they will manually add $25 to my gift card balance.
YMMV but in general my experience with Amazon reps is if your not getting anywhere with the rep ask for a supervisor, they will tell you that the supervisor will say the same thing as whatever they have been saying but tell them you still want a supervisor and the supervisor's usually sort you out pretty quick.
Hope it works for you