The bond, which matures in 2022, will pay a coupon of 1.125 percent annually, the company said in a statement.
The conversion price will be set at a 70 percent premium above a reference price equal to the volume-weighted average price of the shares on the Milan bourse on March 20.
The Italian phone group said last month it would spend 14.5 billion euros in the next three years on laying more fibre optic cables in Italy and upgrading its mobile network in Brazil.