I went to china on 9/3/2015 I was sent back with the same flight to Lagos.

Austin, sorry to hear your bad news, but the Chinese Border Control authority does have the right to deny your entry, even though you are holding a valid entry permit. The decision on whether or not you will be allowed to enter China is made at a port of entry in accordance with Chinese Laws and Regulations and the officer won't tell you what's the reason.