Maybe they stopped it this month. Call customer care and ask if it is still available.
They have hidden option to talk to their representatives so well that it will take atleast 5-7min for you to find. They even change options every few months to make it even more difficult.
If you get option for sim lost then select it, if not then select option of 3g/4g plans.
Within that they have a option to talk to representative.
Really unprofessional practice don't know how they have been getting away with it for so long.