Hey, my friends and me are planning to go to Simatai Great Wall on one day.

We only want to climb the wall and plan to arrive there before 12 pm to get our tickets and than start climbing. In the article it's said that the last m bus goes at 15:30 pm. Is it true? And if yes, is it possible to make the climb before that time or is there an alternative to come back to Beijing after 15:30pm?