French telecom group Bouygues stepped up its bid to buy mobile phone operator SFR from Vivendi on Friday, the last day of exclusive talks between Vivendi and rival bidder Numericable. Bouygues, which also has big interests in television and construction, raised its cash offer by 1.85 billion euros to 15.0 billion euros ($20.5 billion), and also offered 10.0 percent of the new entity worth about 1.0 billion euros.