Sennheiser — replace earphones under warranty

My sennheiser cx 275 s earphone jack got spoiled and i want to return the item for replace as it is under warranty. I bought the product on 13 oct 2016 and it has a two year warranty. I bought the item in amazon. I am not able to get return options in the app as return window has been closed for some reason. I want return the product directly to the seller for replacement or repair.