what happens if the airlines changes the flight which will exceed the 72 hrs visa policy

China Southern airlines has changed our flight which will overstay the 72 hrs tourist visa allowed in Guangzhou. I have contacted the airlines and have informed them that I cannot overstay because we will only be allowed to stay for 72 hrs with the tourist visa. I have not received any answer from the airlines.I have emailed the southern Airlines 3X and called the office here in Brisbane. Still no solution. We also only have 3 days hotel reservation in Guangzho and also other hotel reservation on arrival to Australia which will be affected if our flight is changed from the original itinerary that i have made in March 25 2018. Please advice.