Indigo Airlines — boarding issue

We was at Ahmadabad airport boarding gate not nad and gone to washroom at the time of boarding just started, on return we was not allowed to board in the flight . No announcement and intimation given to us inspite was was at boarding gate from last 1 hr. Flight no 6E 555 from Ahmadabad to delhi on 16.09.17. The company had charged unjustified amount for next flight.