What are my chances of getting the remaining refund quickly?

I booked an apartment in Noida, but the builder overbooked the unit and informed me that they cannot issue the allotment letter, as it has already been sold to someone else. Currently, I only have the booking confirmation and have paid 60% of the total amount directly to the builder’s account. Although they agreed to refund the amount, it has been 1 year and 4 months, and they have refunded only 30% so far, without any interest. At present, they are returning a small amount every two months. What are my chances of getting the remaining amount refunded more quickly? I reviewed the RERA rules, but the resolution timeline appears to vary between 45 days and 3 years.