Also just to inject some personal opinion....
In your subject line, you state that he is already cheating on you. In your message, you state you need proof to catch him "cold handed" and present this surprise "evidence" on him during a counseling session. If I was your husband, I would probably leave you based on this alone, but that's just me.
In a normal and healthy relationship, one would go to their significant other and say "Hey, what's up with the phone bill this month?" Maybe there is an explanation for all of this. Could he possibly be scanning numbers, or calling "cool" phone numbers found on forums?
Your message also states he has problems calling "internet people" all the time. It sounds like the verdict has come down before the jury has even seen anything. Maybe he chooses to make calls when you're not around so he's not judged in this fashion.