MILAN (Reuters) - Telecom Italia said on Thursday it had offered to buy Vivendi's Brazilian unit GVT in a cash-and-share offer that values the broadband company 7 billion euros ($9.25 billion). The offer, which also envisages a merger between GVT and Telecom Italia's own Brazilian unit Tim Participacoes, outbid a 6.7 billion euros offer unveiled by Spanish telecom group Telefonica on Aug.