I'm upset that my partner had this convo with his ex in private
What made you so uncomfortable about them speaking?
Cause she's a lame whore and I don't want to know what they talked about.
What they did was wrong if they were being sneaky about it. If there was something they wanted to say to her they should have let you know.
I'm going to make his life a living hell for this.
I think that you should just talk to your partner about how you are feeling, as it is okay to be upset that they secretly talked to their ex. You should not try to seek revenge though, I am not sure that will make anything better.