Airtel — recharge error in counting of days in packs

Address:

Mumbai City, Maharashtra, 400053

I recharged my phone on 12th september 2018 for 84 days which was to expire on 4th january 2019. I again hot my phone recharged in advance before expiry date. Now after second recharge they are counting 84 day from 1st january 2019 instead of 5th january 2019.
I tried to approach the customer care through phone but failed to do so.
Pl correct the mistake and provide me full benefit of the pack.