The way I see it, there’s nothing wrong with voicing your opinion, especially between games. Saying “hey, I feel like the fantasy of my character isn’t coming to life, is there any way I could get you to take the Charisma score of my character in greater consideration during social interactions going forward?” after a game is a great way to deal with that. That said, there’s only so much that Charisma can account for. No matter how charismatic you are, you won’t persuade a king to give up his kingdom. Your DM likely thinks your arguments are just too weak for you to persuade someone, regardless of your Charisma. Maybe their expectations regarding your wit and roleplay are too high, or maybe you need to re-evaluate your expectations of what is possible in your game.