Airtel — call charges on special numbers

In my monthly postpaid paid bill for the periodi ending on 25 may 2019, i have been charged rs.74/- for calling 1860 series numbers in-spite of having a unlimited local and std calling plan.

On reaching out to airtel i was told that these are special numbers and i am liable to be charged inspite of having a unlimited calling plan.
However, there is no such mention in the tariff rates mentioned in my monthly bill.
Lakshmanan shanmuga sundaram
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