Is it at the bottom of the top tube, right in the middle, a straight line ?
Can you make a better picture? I cannot see if it's a crack or just the place where the mold came together.
How long do you have your frame ?
You have to contact your seller and claim your warranty. But have good quality pictures!
Ask him for options: send back your frame and get a replacement (you have to pay shipment to China) or make a deal with the seller and let if fix a local carbon repairer.