ATT Inc said on Monday it had sold all of its equity in Mexican telecoms giant America Movil , which is controlled by billionaire Carlos Slim, to Slims real estate firm, Inmobiliaria Carso for $5.57 billion. ATT said in a filing it sold the stock comprising 72.8 million L shares and 5.74 billion AA shares. On Friday, Inmobiliaria Carso said it would buy the stock, which ATT said in May it would sell to help it gain regulatory approval for its purchase of DirecTV .