Tango Smart subscription
Calls you make in VoLTE via 4G are included in your subscription. They will be deducted from the voice and SMS units and will not use up your data traffic pack.
If you have used up all the voice and SMS units included in your Tango Smart subscription, you will be charged for the VoLTE calls via 4G at the normal rate applicable to a call.

Tango K.O. subscriptions
Calls you make in VoLTE via 4G will be charged by the minute at the normal rate applicable to a call made with a Tango K.O. subscription