Spice Jet Airlines — Refund for cancelled flight not received

This is regarding the flight from Dehradun to Pune dated 25th July 2022, which was cancelled by Spicejet. The associated PNR is D8SFJS.
The flight was actually rescheduled by them to the next available slot, and we were allowed to cancel it if we wanted. In case of cancellation, they promised a full refund within 21 days. But, we have not yet received any intimation from SpiceJet about the same, even after the period of 21 days has passed.

Can we get the refund plus the interest amount applied to it as soon as possible? If we don't get any reply on this, we will have to approach the court for registering a legal complaint with them.