I want to register complaint against a Nokia Care Service Centre

I handover my Nokia Xl to Nokia Care – Harmony Audio Bombay Pvt. Ltd. , Mumbai at 29/09/14 , when it was under Guarantee . and they said they’ll return it within 15 working days . but now its almost 20 days , and its still not repaired.

Please let me know contact numbers and email of the Nokia India Upper level customer officials and grievance cell.