TypeError : props.navigation.getParam is not a function. In(props.navigation.getParam('name')

use props.route.params.name this is working

 this.state = {
    person:{
      name: props.route.params.name,
      phone: props.route.params.phone,
    },
    textMessage: ''
};

In class component props can be access using this keyword. So try this :

export default class ChatScreen extends Component {
  static navigationOption = ({ navigation }) => {
    return {
      title: navigation.getParam('name', null)
    }
  }

  constructor(props) {
    super(props);
    this.state = {
      person: {
        name: this.props.navigation.getParam('name'), // access with this.
        phone: this.props.navigation.getParam('phone'), //access with this.
        // name:'Raushan',
        //   phone:9931428888
      },
      textMessage: ''
    };
  }
}