MILAN (Reuters) - Italy's biggest phone group Telecom Italia confirmed its guidance on Thursday after reporting a better than expected improvement in net debt, even as stiffer competition in its domestic market continued to take its toll.Telecom Italia (TIM) said its net debt at the end of September fell to 24.3 billion euros, with a reduction of 958 million euros compared with the end of last year, achieving its full year debt target three months ahead of time.The incumbent said its organic..