Correct. Service Validity and 'Pack Validity' are completely different things. As of now, the cheapest to get 28 days 'Service Validity' is the Rs 79 plan. For Vi, in some circles, the Rs 49 plan still provides 28 days validity, but in few circles, it has been reduced to 14 days Service Validity.
Btw, guys I had a another question. I had 3GB Data pack, with 'Pack Validity' of 28 days valid till 20-Aug-2021. On 29-Aug-2021, I have recharged with Rs 399 Unlimited Plan, giving me validity till 13-Oct-2021 (56 days). However, the 3GB data pack valid till 20-Aug-2021, lapsed, and its validity didnt get extended. I thought that if we recharged prior to plan expiry, the validity of data gets extended in Vi. What is different in my case here?