ok.. so I visited the nearest rel digital store with my old dongle..
1. sadly they didn't have stock of jiofi3 (the one with the screen)
2. No matter how many jio Sims you've got, you have to buy one sim with an additional payment of ₹408 with the new jiofi purchase.. [This is the normal procedure]
3. You'll get 1500/- off on your old dongle so as per post no.1, you'll get a jiofi 2/3 device for ₹499/-
The store i visited had only the old jio fi device, the one that has no screen so I didn't buy any for now..
This is a fairly good deal given that I've got my dongle for 1.7k back in 2012, it's 3g only and has no wifi!!