if u have call recordings then submit the call list from your cell phone bill. The call records shall be obtained by Investigating officer ie., Police. After giving private complaint, make a request in writing to the Investigating officer or court to obtain Call list from the service provider such Idea/Airtel/ BSNL etc. It is importanat to request the court or Investigating officer to obtain call recording data from the service provider, as the service provider will not keep the call record data for 3 years only.
Then pray the court for testing of voice recording incase the opponent claim that the voice is not his own.
call records relating cellular phones proof & authenticity
State Vs Navjot Sandhu AIR 2005 SC3820