What if someone wants to migrate from Prepaid to PP+ before the existing plan expires. Would they adjust the bill amount on a pro rata basis. If not, I think they should because not all child connections have same plan expiry date. 

@Srivatsav As far as I know, No. Prepaid to PP+ migration forfeits any existing plan benefits. Customer should be self aware and responsible in this case.

On other telcos any existing Main BAL on prepaid will be credited to postpaid account bill. 

I am seeing unbilled amount for my plan. I have opted for 399 plan. What is this unbilled amount in jio postpaid. Its just 2 days i have activated the number.

@Mohi Would you be able to share more info regarding the unbilled amount or billing cycle or screenshot of the same(masking your number)? Then it would be easier to understand and help.