If your question refers to programs that are not part of OPM but are under another federal department, you should reach out to that department directly. You can find contacts for all federal agencies on the USA.gov website's Index of U.S. Departments and Agencies.
The U.S. OPM OIG can be reached by phone at the following number:
(202) 606 - 1200
If you like to contact us via mail, you can do so at:
1900 E Street, NW
Room 6400
Washington, DC 20415-1100