Seeking realistic advice for a seemingly endless problem...?

I am a happily married mother of three. My husband and I get along great, you could say we're best friends. He's a great dad, a little lazy at home, (but show me a man who isn't), and a good provider. I still find him extremely attractive, and our life is still great after 9 years. I've never been a jealous person, and I've never suspected him of infidelity, never had a reason to. Until a couple of years ago. He started having phone conversations with other women, mostly that he works with. The convos really only take place while he's at work (he's a police officer), and the only reason I know about them is because I pay the cell phone bill. It's been about four different women now, two still currently. I don't think he's slept with any of them or anything like that, but there's been a lot of talking going on. The argument always goes the same way; I ask him about it, he says they're friends from work, bitching about work, etc. I tell him it's inappropriate, he accuses me of not trusting him. That's not the case, I just feel like if the shoe were on the other foot, he would be a little upset as well. One of the women used to call him some 10-15 times during his shift. He says out of boredom, I think she was/is interested in him. He claims it doesn't matter, b/c he isn't interested. He also agreed that he talked to her too much, and it has really slowed down. But it hasn't stopped. There is another woman he speaks to occasionally as well. My dilemma is: I don't want to be one of those psycho wives that "won't allow" him to so much as speak to any other woman, I don't like ultimatums. However, it really bothers me that he still talks to them, platonic as it may be. Am I being silly? How do I toe this line between "cool" wife and "crazy jealous" wife??