First thing you should do is enter the warranty number on the back of your pack into the Hobbyking site for warranty purposes and start a thread on their forum in the "Support section" section under "Order support". Try to put up photos of the battery and try to show voltages with a cell meter.
I just ordered $600 worth of batteries from the Aussie warehouse and one of my 5S had a puffed cell that was only reading 0.7V. Anyway I tried doing the whole RMA thing but it gave me a Chinese address to ship back to. Wasn't keen on sending back a faulty battery through air mail so I got onto the Hobbyking CS and wrote them an email. They told me to take pictures of the battery and with a cell checker to show that indeed a cell was low on voltage. It did take a few day for it all to come together but I'd say 6 days later they credited my Hobbyking account with $65.00. I did offer to send the battery to the Aussie warehouse in Sydney via road transport but they said it wasn't necessary. All in all not too bad of a service from a China based shop. Most times I have purchased something faulty from anywhere in China I was pretty much hung out to dry with not even a reply to my emails. Now I have a free 4S Battery instead of the 5S one I needed but who is complaining when it's free.
If you are interested in my dealings with Hobbyking have a read of this thread.
CLICK HERE (thats my thread). Try to be nice and polite as possible. Being an ass and just jumping up and down isn't going to help you much. Write a polite post and get the mods on your side and they will not let your issue rest for too long as they will keep bringing it to the CS Patrols attention. One of their mods "Beladog" is a top bloke and will do everything possible to help if you are polite and act civilized. Lots of people get on there and start slinging sh1t at Hobbyking then they wonder why their issue hasn't received any attention.
I know it's all a bit of a hassle but if they sent out a new battery (or what ever else) after someone received a faulty item then they would be out of business very quickly. They have to make sure they aren't being scammed.