I would write them an email stating how you feel and ask if it's just not eating, or what the issue is and let them know you may want a refund since they are not being helpful. May just be that the hatchling isn't eating and the seller isn't comfortable sending it to a new home yet. Hopefully they will be upfront and honest about what the issue is. If they don't get back to you with an explanation then I would start asking for a refund.
Haha! Foschi beat me to it.