Someone Help Me Out

I graduated from school in Dec 2005 after a year spill-over session (should ve grad. in 2004), although i wrote my last exam in August 2005. While waiting for my result and NYSC processes, i got a job with an oil servicing coy in PH. The job happened to be related to my field and i was doing fine. Cos of the job, i missed my NYSC in 2006 and Feb 2007. By Sept. 2007, i went for the NYSC (their was "militant break" then). During the NYSC program, Jan 2008, i was called back to work and with fellow corpers help and NYSC officials, i passed out in Sept 2008 without any wahala, "money change hand though".
The main gist is this, between Sept 2007 and Sept 2008, i should be serving in Niger state, but i was actually on a project in Niger Delta. Incidentally, this project forms the background and most important part of my job experience, i just cant throw it out. How do i explain this period during interview? Do i say the truth, as in shld be serving but some1 covered for me? Shld they really care? at least the NYSC cert. is their and verifiable.
Please i hope u guys understand my story, kindly help a brother out. I need the NYSC cert., i need the job experience.

Tell them the truth afterall they're interested in the experience.