What is IUC and why has Jio started charging for voice calls?

Interconnect Usage Charge of 6p/minute, proposed to be scrapped from 2020, is paid by an operator to rivals for connecting calls of its users. As TRAI considers continuing the charges, Jio stands to lose because 64% of its traffic is outgoing. Jio is charging for calls to recover IUC as it claims receiving 25-30 crore missed calls from rivals daily.