If it dies you certainly should call them on it. My Annabelle hydrangeas still have lots of leaves and green flowers and I'm in the Atlanta area. SC should be the same if not more growing time for this fall.

What mail order place was this? I can probably guess if it is in SC and if I'm right I quit ordering from them 20+ years ago due to small size and half dead plants if not dead on arrival.

I would have dunk it in water as soon as I got with all the soil it had to rehydrate the root ball. I would call again and complain. Especially if it dies.

Under normal circumstances, hydrangeas should not go dormant this early in SC (unless they are forcing them and that would be unexpected). Over here Annabelle goes dormant in Nov-Dec.

Luis

Another suggestion: do not put an order to be delivered during this time of the year. If the plant got driven thru Texas, it got a bounty of 100 degree temperatures; hopefully it was air conditioned.