GHMC — overflowing manhole

I would like to enquire if the cleaning of manholes in the residence premises is charged and if yes, what is the cost for getting it done by a septic tank vehicle?
On what basis are we charged, is it dependant per residence wise or number of manholes per residence..
Kindly respond to my query so that we know how to go about it.. As me and my neighbour were charged a certain amount for resolving our overflowing manholes.
Thank you