can we port from Vodafone postpaid to xyz prepaid?

Yes….. No such restriction..

Just ensure that You clear all Dues of Voda Postpaid

then in that case, first Port Post-to-post ….. few days later, within the same Operator go for Post to Pre conversion

Even other operators are playing the game of not losing fixed revenue of postpaid users.

They wont let you go. Doesn’t matter how hard u try.
I dont knw why they are rejecting your application but most of the time they will ask for Rental or Electricity bill with your name to port to prepaid.

first convert from Voda Post to Voda Prepaid , after that u can move in any operator . This is the best solution .

postpaid to prepaid, prepaid to postpaid, GSM to CDMA :- Porting is possible between different service providers and also between different circles.
Read this → ( http://www.trai.gov.in/sites/default/files/Cust... )
If you meet the eligibilty conditions, and still the mobile service provider denies port request, give a complaint to them.
If not solved, then post complaint on pgportal.gov.in

Vodafone is well known for rejecting port requests on flimsy grounds.

first convert from Voda Post to Voda Prepaid , after that u can move in any operator

But id on this no is another one and billing address and alternate no is mine

I ported my idea postpaid to vodafone prepaid no problem occured
Ya in case of you have taken premium number from them by asking for postpaid connection they will reject your application for few months
Happened both situation with me on idea postpaid