Airtel — 4g pack 399 with unlimited calls & 1gb/day data for 70 days

Recharged with 399 on 12 oct 2017 for 4g pack valid for 70 days, but today
I was unable to make a call. Then i contacted the customer care and they say it is valid only for 28 days. If it was just for 28 days, why will i go for this option when i had many great offers from other service providers.
Even today when i google for airtel 399 pack, it explains as follows :

"now, airtel offers 399 with unlimited calls & 1gb data per day for 70 days for prepaid subscribers across india. Airtel also announces offer packs 449 & 293 which offer unlimited voice and 1gb/day data for 70 days while using airtel 4g network."

Reference link :
https://www.newstelecom.info/2017/04/airtel-offers-4g-pack-399-with-unlimited-calls-1gbday-data-for-70-days/#.WgQ1uteWa70