Upgrade to Enterprise Edition

[taqvi]

I am trying to upgrade to Magento 2 EE after installing Magento 2.3.1 CE using this Image. But there is no luck yet. What I did is:

1. Updated access keys in auth.json with Enterprise edition access keys.
2. Updated composer.json (Changed name, type, license and "require")

{
    "name": "magento/product-enterprise-edition",
    "description": "eCommerce Platform for Growth (Enterprise Edition)",
    "type": "metapakage",
    "license": [
    "Proprietary"
    ],
    "config": {
    "preferred-install": "dist",
    "sort-packages": true
    },
    "require": {
    "magento/product-enterprise-edition": "2.3.1"
    },
..........................
..........................
}

and executed:

composer update

but it removed many dependencies. I also tried upgrade from Magento Backend, as described here [https://devdocs.magento.com/guides/v2.3/comp-mgr/upgrader/ce-ee-upgrade-start.html]
but it says 'you are already using latest version'. Where is problem ?