If you're sure you don't want this job, there's nothing wrong with canceling, but you'll want to be extra sensitive because it sounds like you already went to an interview for the same company? I'm surprised that they don't know you've already been in for the interview. Let them know right away that while you thank them for the opportunity, you've already interviewed with their organization for a role you think you'd be a better fit in. Then wish them the best of luck in their hiring process.

Good luck!

Take the interview, if they ask for references, tell them you will send them

but DONT CANCEL

Just lie and say you won't be coming to the interview because you got a job offer from somebody else

You'll be sorry.

Jobs are hard to get these days. You're going to think back on this moment and realize it was a very bad choice to claim you "didn't have time" to call three people and say "Is it OK if I use you as a job reference?".

On the other hand, when this person called you, why the heck didn't you just say "Oh, I've already interviewed with your company". That might be what you need to do -- check back with him and make sure he knows you've already interviewed with someone else there. He may tell you not to bother coming in, or he may tell you he still wants to see you. You'll never know unless you call.

Don't cancel.

Go, and do your best. References are easy to come by -- use former employers, former professors, former co-workers, close friends. Do not use family.

It is unlikely that the people you just interviewed with will know that you're there for another interview, and even if they do, who cares?

You should go and give it your best shot, even if you are no longer interested -- even if you don't get the job, if they like you, they may contact you later if another position opens. It happens all the time. But there is zero percent chance of that happening (and of you getting hired in another branch of the same company) if you ditch the interview.

Go for it.

Tell them that you found something else