I am having a problem drawing the "Game Over!" text once the user is on the last tile.

This is what I have:

The Update and drawText methods are in a class named turtle:

public void Update(float scalingFactor, int[,] map, SpriteBatch batch, SpriteFont font)
{
    if (isMovable(mapX, mapY - 1, map))
    {
        position.Y = position.Y - (int)scalingFactor;
        angle = 0.0f;
        Program.form.direction = "";

        if (mapX == 17 && mapY == 1)// This is the last tile(Tested)
        {
            Program.form.BackColor = System.Drawing.Color.Red;
            drawText(batch, font);
        }
    }
}                    

public void drawText(SpriteBatch spritebatch, SpriteFont spriteFont)
{
    textPosition.X = 200; // a vector2
    textPosition.Y = 200;
    spritebatch.Begin(SpriteSortMode.BackToFront, BlendState.AlphaBlend);
    spritebatch.DrawString(spriteFont, "Game Over!!!", textPosition, Color.Red);
    spritebatch.End();
}

This update is in the Game1 class:

protected override void Update(GameTime gameTime)
{
    // Allows the game to exit
    if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
        this.Exit();

    turtle.Update(scalingFactor, map, spriteBatch, font);         

    base.Update(gameTime);
}

I have also added the font content to LoadContent:

font = Content.Load<SpriteFont>("fontType");

What am I doing wrong? Why does the text not want to show on game completion? If I call the turtle.draw() in the main Draw method. The "Game Over" text stays on screen from the beggining. What am I missing?

Thanks