Big problem?

So I just enlisted in the Air Force. I had DEP'd at one time but had to drop out for personal reasons. A lot of my info was still the same. When I went to MEPS yesterday they were not expecting me to finish that day so they didn't have my file. I had to go over it on the phone with my recruiter. The names on my security clearance reference form were the same as last time. One of the people on it is no longer someone I really consider a friend. We were best friend at the time though. and yesterday I could not think of anyone else to put on the list. So can I change this now, if not what questions do they ask when they call people for a security clearance.