Bharti Airtel Questions

Hi VPs, I have a question on consolidated P&L and BS of Airtel. ( Source Money control)

in P&L, Depreciation in years FY13,FY14 & FY15 is reported as around 15K.

But in Balance sheet, in the same years accumulated depreciation is changed from 37K to 60K. as per my understanding Depreciation should add to accumulated depreciation. I have seen this kind of scenario in other companies as well. Can any one please explain why there is a difference.?

Thanks
sridhar