get data from postman request with data in body

I have a postman request with some data in the body like that :

{
    "informations" : {
        "contact" :[
        {
    "email" : '[email protected]',
    "phone" : 0111111111,
        }
    ]
    }
}

I symfony side, I can get theses data with :

$data = $request->getContent();
dd($data);

But I can’t access to the “contact” array, I tried this :

dd($data['informations']['contact']);

And I get this error : Warning: Illegal string offset ‘informations’

What is my mistake ? thanks