the model does not connect

I am using the latest version of Codeigniter, the NetBeans program for the code and XAMPP.

In the controller I have the following code (it's called Sesion.php): 

PHP Code:

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class Sesion extends CI_Controller {

     public function __construct() {
        parent::__construct();
        $this->load->helper('url');
        $this->load->library('session');
        $this->load->model('usuario');
        
        
    }
    public function index()
    {
             if (!$this->input->post()) {  //SI NO HAY POST  
            $cuerpo['c1'] = $this->load->view('form_sesion', '', true); //CARGA LA VISTA
            $this->load->view('plantilla', array('cuerpo' => $cuerpo));
        } else { //SI HAY POST 
             $usuario = $this->usuario->ExisteUsuario($this->input->post('user'), $this->input->post('pass'));
            //MIRAR SI EXISTE EL USUARIO DE QUE TIPO ES
            $this->Entrar($usuario); //MANDA A SU CONTROLADOR
        }
} 


In the model (it's called Usuario.php): 

PHP Code:

<?php

class Usuario extends CI_Model{
    
    public function __construct() {
        parent::__construct();
    }

    
    public function ExisteUsario($user, $pass){
        if($user === "usuario" && $pass == "admin") {
        return "vale";}
    }
} 


The error:

PHP Code:

An uncaught Exception was encountered
Type: Error

Message: Call to undefined method Usuario::ExisteUsuario()

Filename: C:\xampp2\htdocs\matsa\application\controllers\Sesion.php

Line Number: 24

Backtrace:

File: C:\xampp2\htdocs\matsa\index.php
Line: 315
Function: require_once 


Note: the function receives the two variables perfectly

I think that it should work but I do not know what happens, I hope you can help me. Regards!

@adanwaky,

It might be that the name of the model needs to have a capital first letter.
Instead of $this->usuario->ExisteUsuario() it might need to be $this->Usuario->ExisteUsuario
also...
instead of $this->load->model('usuario'); it might need to be $this->load->model('Usuario');

The reason I say this is because in your error message it states that... Call to undefined method Usuario::ExisteUsuario()
DID you notice the capital first letter of the Model?

Also, any reason why you don't return a value of FALSE if the model function if condition is not completed? I always try to either return a value or FALSE from a model so that I will always know if it was successful or not.