MakeMyTrip India — Not able to use Makemytrip wallet amount

Website:

www.makemytrip.com

On one international flight booking, I received 2500 my wallet balance with the expiry date of 3 months from the date of booking. When I login, I can see the mywallet balance of 2500.
Eventually I happened to make some other international flight booking. On the payment page, it showed me the message that ' I have 2500 my wallet balance, please login to use'. To my surprise, when I logged in it said I didnt have any money.
I tried to log-off/login, but of no help. I tried to book after some time but that too without any help.
Called customer care 4-5 times. Every time they kept on transferring my call to multiple dept, but none seems to care / or provide any resolution. Each time they disconnected it after multiple routing.

Is the mywallet some kind of fraud ? Has anyone faced the same issue?
For sure, will not use makemytrip again.