I sent a package to china. It shows that its in Shantou City and waiting on user to pay tax. The recipient has said they don't know where to pay. How do they pay the tax?

Thank you.

CH189713997US
The receiver said he was not contacted. His phone number is 86 139 0794 2515
Is there anything I can do as sender?
Thank you.

After translating it says the status of the package has left customs and is waiting for users to pay taxes. Do I have to do that? If so, where and how?

Thanks