Vishal Mega Mart — No proper information about product

Today I have purchased in cishal mart shivamogga. Monaco biscuit-1 packet in offers it was written buy one get one...actually in all other supermarket if their is buy one get one offer and we purchase only one product they bill will be done half.but same was not done and neither I was informed to take 2 biscuit packs to avail the offer.after paying bill while checking I asked the billing person but he told customer have to tell them about offer of their mart... so called reputed company should update their staffs.even I have raised complaints in customer care service today only, but no use.he told store person will contact but it was not done.Do not cheat customers in name of offers.