Vodafone India — convert postpaid connection to prepaid connection

Address:

Ahmedabad, Gujarat, 382350

1. I wanted to convert my postpaid connection to prepaid connection of vodafone sim.
Hence i have visited vodafone store on 25/09/2017 at bapunagar and submitted my documents there.
They told me that within 48 hours your connection will be converted to prepaid.
My postpaid sim was not convinced so again i have visited vodafone store on 7/10/2017 again i got the same response from them as within 48 your connection will be converted.
But still my sim wasn't converted. So again i visited store on 14/10/2017, at that time, they told me that you have to submit documents again. Hence i have submitted documents again and got the same response like above.
Still my sim isn't converted to prepaid.
Today i will visit vodafone store but before visiting, i think, i should log a complaint against vodafone and it's store.

My postpaid bill is increasing due to above problem.
Please help me out this problem.