Cleartrip — Change of date not done- ticket cancelled arbitrary

Address:

C3/ 247 Janakpuri New Delhi

I booked a Singapore- Delhi flight for Vistara Airlines. After a week i requested for change of flight date through email and consented to pay all charges. Cleartrip did not act and instead cancelled my ticket. After two days they sent me email that my refund has been processed and the sum refunded is Zero.
This is very strange. If refund to be paid is zero, then why one will cancel it.
I wrote back that they can restore the validity of my ticket, and i would travel on the earlier booked date.
They are not replying.
My date of travel is June 01.