Defamation of Government Officer while performing duty

Sir, I am Postal Officer, In recent changes in postal policy, all parcels booked at retail counter or by bulk customers, there were charge as per their volumetric weight based on its width, height and length. This is applicable for PAN India level. But one customer, whose parcels were rejected to book as per old pattern, complained at all higher level including ministry quoting my name, as he destroyed his business and manipulated my image. During performing office duty, i was bound with guidelines available with me and system also does not allow to book any parcel without entering the dimension detail. Can I lodge complaint against this customer of defamation. Please guide