Popshop online sale purchase app - Demand of more money in addition to as cited in advertisement

Popshop is a Indian app which provides ayurvedic material on low prices. Recently I booked an articles amounting to rs ***/- as shown in advertisement. After booking the article on ** March ** I didn't get the same upto first week of this month..where delivery of articles was shown as free. I email on the customer service and he directed to call the supplier...the supplier whatapp me to forward **** rupay in addition to that I already paid..lateron I grade the app a bad experience and the supplier refunded me my amount...I only want to know when an article is placed for sale with its amount as two hundred only why the supplier trying more money...