Cheque bounced & issuer refused to accept notice, plz help

One person with whom we had good relations took 3 lakh rupees from us as a loan against which he gave us post dated cheque as a gaurantee. When the date came he developed an ill-will and cheque got bounced for the reason of insufficient balance. Clearing memo date was 20-May-2019.

We sent him legal notice via registered A.D. and he refused to accept that notice as per the post-man, postman says he has returned the notice back to sender (we) mentioning that receiver is not accepting the notice. Now please suggest what can we do. Its only 3 days left now, as per my knowlegdge we need to send notice within 30 days of clearing memo date issued from bank. Any help will be appreciated.