Are you tied to a contract with that university? If not, I would say walk out and find a better job. However, I have a sneaking suspicion it's not that simple in China!
Have you requested a meeting with the head of department or whoever is in charge or who you report to?
Did you get the position through the company you did the CELTA with? If so, I would certainly take it up with them as it's clear the job is not as advertised.
Are there any students in the class who apper at all engaged? If there are, I would concentrate on them, if necessary ignoring the ones who mess around and leave the room. If it's a required subject, it's not surprising that they don't all want to be there.
I'd ignore the advice about the textbooks but if you only have one it will be difficult to use anyway. Can you download and print exercises from the net and hand them out to those who are interested?
If absolutely none of them want to learn and the university doesn't care then I suspect you're in for a rather long and boring year. At least you're getting paid!
I hope the situation improves for you.