Why is my ex-husband still denying his infidelity when he had it tapped on his dig. dictaphone?

The whole thing is clear as day to hear and very disturbing to have found. However it was not with another woman but a man. He is trying to tell me that I have lost my mind and that he is eating a "subway sandwich and going over speed bumps in his car"! I wanted to believe him but......he is clearly with someone and is very explicit. I realize the humiliation he may be feeling. He also has an oxcyconyin and alcohol problem. I want to move on best I can with my life but he continues to call my cell and leaves horrible and long V/M! Why won't he at least say hi to his children? Any insight would be greatly appreciated.