India Post — dishonour of the cheque of post office saving account by the bank

I have savings account in post office with cheque & atm facilities, but it is very much regretted that the cheque issued to 3rd party was dishonoured by the banker of the party (Copies of cheque as well as return memo of the bank attached herewith for ready reference), which gives a bad name to me & adverse effect to my reputation. Please let me know who is responsible and what is the use of cheque book issued by post office whenever its cheques are not honoured by a scheduled bank. Kindly look and advice.