Vodafone India — repeated calls regarding an unrelated bill and rude behavior by the representatives

Over last 3 months, i have received atleast 30 calls regarding due payment of an erstwhile colleague of mine which was a nepali resident and has left india around 3 months back and with whom i am not in contact with anymore.
Even after telling this to your customer care personnel it has not been taken into consideration. I had taken this issue with customer care but to no avail.
Also the behavior of the customer care representatives is very rude, short of abusing they have said everything. They even threatened to disconnect my connection.