Hi,
In automatic focus mode, focus going in and out is not an unusual condition, under certain lighting conditions and certain subjects.
Go to manual focus mode and focus manually. I assume this will fix the problem. If it does not, start raising hell with the seller, because this would be a fundamental flaw.
Also, see my last post to you under General Questions, subject Shutter Speed, where I recommend that you manual focus for the interview.
You need very good luck today, so BEST OF LUCK!
REGARDS ... TOM 8)