I just got a call about having a second interview for a job I don't want. I don't really want to go back there, and I have never had to do this "turning someone down professionally." It's not like I make a ton of money right now, but this place is too far away from me for not enough return on money and other intangible things. But they just called me back, and I chickened out and let it go to voicemail. I'm glad I did because I don't want to go on a second interview at all and have no idea how to say "sorry not sorry no thanks good luck BYE."

Is there a polite way to do that? I'm supposed to call back, right? If they call me, I have to call and not email them back? UGH I am so confused.