Vodafone Idea — Retrieving old phone number

I was using this number which got deactivated. When I tried reactivating, I was told it was now in someone else's name and I would be able to get it only when it was abandoned by the current user.
Now it is not owned by anyone, it has been confirmed by the v-i customer care executive. However, when I request that it be resold to my name, neither the online nor the v-i store execs are able to help.
I want the old number to be reallotted to me.