Can I cancel flight after date change and still get some partial refund?

I booked an Indigo flight through MMT, with flexible date change option. I want to change the date of the flight due to my schedule, but I'm not sure of the specific date. Hence, I was thinking of changing it to the tentative date. Will I be able to cancel my flight and get some refunds post a date change if needed?

P.s. mmt is charging some 3600 rs for flight cancellation on a flight ticket of 7200rs for now, and the charge would only go up if I cancel it around the date of departure.

I've tried contacting both indigo and mmt, but both of their customer care number take me to only automated messages and not to any actual person.

Thank you