Using 2 different airlines

I'm traveling from Manila to Guangzhou on the 19th of September upcoming with Cebu Pacific. My flight will arrive at Guangzhou around 21:30. On the 22th of September I will be traveling from Guangzhou to Cambodia with PRC Southern on an early morning flight 8:45. If I will be entering Guangzhou with Cebu Pacific Airlines, and leaving Guangzhou with PRC Southern, am i still able to use the 72hours free visa? My tour operator is telling me that I have to enter PRC with PRC Southern so I can make use of this 72 hours program. Is that true? I have an European passport.