MUMBAI, March 17 (Reuters) - Bharti Airtel Ltd, India's biggest mobile phone networks operator, has agreed to pay 44.28 billion rupees ($664 million) to Videocon Telecommunications for radio frequencies in six service areas, trumping rival Idea Cellular's smaller deal for the same spectrum in two service areas. Bharti, India's largest mobile phone operator, said on Thursday it will take up spectrum in the 1800 Mhz band from Videocon in Bihar, Haryana, Madhya Pradesh, Uttar Pradesh (East and West) and Gujarat.