Indian Citizen 15 hours layover in Beijing

Hi, I am going to New Zealand on Air China and have 15 hours layover both the times in Beijing. Can I avail Free transit and go outside the airport for Great Wall tours? I am confused because mumbai centre for visaforchina.org replied to my query as this "within stopover at the airport you cannot leave the airport".

Kindly help and suggest any steps to take (like getting a letter from embassy if possible), I am travelling in 2 weeks.