Communicating with someone isn't cheating. Dictating who your partner should and shouldn't talk to will not help him want to be with you. And you can't sustain any relationship without trust. He chose you, he's with you - that doesn't mean that he can't have female friends.
It would certainly result in a conversation - trusting him is YOUR decision. If you can't, then you leave and move on. I hate to be so harsh and blunt about these things ..
I'd just stop speaking to them and let them talk to whoever they want
but you clearly aren't important in their life so it wouldn't matter? if getting hurt and not feeling good enough is important to you then that's your choice lol
They probably ain't,,,,,yet
That was actually pointed out to me once and I stopped after she told me how it made her feel,,,,,you could try that instead of just telling him to stop