Make My Trip Pvt Ltd - Not provided alternate flight for cancelled flight

I had round tip booking from Mumbai to Mahe, Seychelles (**th Feb - *th March). On *st March, MakeMyTrip sends me a message that return flight got cancelled and you will have to cancel the ticket as the alternate flight was not available. Due to limited network availability, I was not able to confirm the same with the airline carrier. Because of that, I had to cancel the ticket and rebook the same on an urgent basis at very high prices (Rs **,***). After coming back when I contacted the airline they told me that they have provided an alternate flight to customers and I observed the same at the airport too and told me they have no clue why MMT said that to you.
Secondly, the total cost of the ticket was Rs. **,*** with effective cashback of Rs *,***. The refund I am getting is the only Rs. **,***, they are deducting the complete cashback and are also charging the convenience fee for the cancelled part.
Thirdly, I didn't get any fare break - up as in how much I paid for Mumbai - Mahe and for Mahe - Mumbai, so there is no way for me to validate whether the cashback they are giving to me is correct or not.
Fourthly, I have followed up with them multiple times with the matter, and it has been ** days till now and I am only hearing that they will get back to me and have not received my money yet.
If you feel my complaint is valid to do let me know, I will attach the relevant documents too, along with the cancelled ticket, chat where they told me to cancel the flight and so on.