Make My Trip - Wrong cancellation charges taken

I cancelled my flight of **th Mar'** on **th Mar'**, directly with the Airlines. I reported the same to MMT on **th Mar using their app and got a confirmation email stating that they have received my cancellation request and would refund my money in ** hours. The Airline confirmed that the refund amount is Rs ****, however, MMT never initiated the refund, in fact, until I followed up on *nd April for the refund, this trip was shown as completed on their app/website.
MMT has refunded only Rs *** and fail to explain why they have not refunded my full amount. MMT cancellation charges would not apply as I cancelled the ticket directly, they didn't even get in touch with the Airline before the journey date to check my ticket status, why they want me to pay cancellation charges when they have done nothing to cancel my ticket. The irony is that they sent me a mail on **th Mar asking for feedback after my successful completed journey.
I have had multiple calls and chats with their customer care without a resolution, they assured a manager would call, someone calls me but I wasn't able to take the call and asked them to call back again, but it's * days and no one has called me.
I have faced similar issues last year as well with MMT when they delayed my hotel booking cancellation refund abnormally. Please help me get my full refund.