Off duty official work procedure

Respected Sir, I am Mr. Roshan works in a MCGMs Fire Brigade Department as a fire Officer. when officer attends any incident (Fire call) he has to write report of that incident and dispatch it to administrative office where senior officials check it and approved. one of my senior most officer found minor mistake in report which was written by me and informed our Control Room to transmit message for me to come his office for correction in that report off duty.(mean adjust shift duty and come to office off duty). as his office was far away from my residential and working address and duty to family responsibilities it was very difficult to me to go to his office. so I called him 2 to 3 times to report my inability but he cut my call and didnt respond. Now the officer has issued me memo and asked me why to not take disciplinary action as u have not followed by orders. Respected sir please guide me to face the situation. how to answer the memo? please guide me and tell me the laws and concern acts