It is no doubt a civil matter and not a criminal offence.
On the basis of the transactions and communications between the individual and the society, it clearly indicates that the individual has purchased the allotted plot by paying the requisite amount.
The society has not denied the receipt of the amount and has even volunteered to return the amount with interest.
This evidently proves that there was a payment made by him, hence he can very well approach civil court with a claim without delaying it any further