Vodafone India — Postpaid to prepaid conversion

I submitted relevant papers to baguiati vodafone center in order to change my post paid no [protected] to prepaid since i am going to stay in bangalore for next two years, they have issued me prepaid sim also and assured me that my prepaid no will be activated within 72 hrs. But the prepaid service was not started as assure on .14/6/2015

ultimately i had to continue with postpaid service and incurred extra expenses,