Proof of transit visa prior to flight to China

I want to fly from Manila to Guangzhou with airline A then within 72hr fly from Guangzhou to Kuala Lumpur with airline B. My understanding is that it is okay to enter and exit using different airlines and I can get the transit permit when I get to CAN airport. No prior arrangements necessary. However if airline A requests to see a Chinese entry permit before they let me on the airplane, what document can I show to prove I can get the transit permit when I arrive? I ask this because I had this specific problem with Cebu Air and they insisted on seeing an entry permit before allowing me on the flight, which I did not have and they refused my boarding. Obviously I will use another airline next time.