Who do I contact if I have a question about a job opportunity announcement?

From USAJOBS Help

For questions related to a particular job announcement, contact the hiring agency. The agency contact information may be found at the right hand side and in the lower portion of the job announcement. If you have already applied to the position or are in the process of applying, go to "My Account" and view the job summary in your application history. You can also contact the human resources office of the hiring agency for additional assistance.

TIP: You can use the control number to locate a particular JOA, even if a position is closed. If you have the control number, you can place it at the end of the job view URL (http://www.usajobs.gov/GetJob/ViewDetails/) and you will be able to view the announcement. Otherwise, if you have the job number, provide the announcement number to our help desk and we can provide the announcement's web address. To reach the help desk, click Contact Us.