After trying some other websites I once came to amazon and after using it I never tried any other online shopping site.
They always delivered me before the time of delivery.And moreover the details of the product are genuine and exact.
They have never disappointed me.I once ordered a wrong product and needed to replace it.I just had to inform them once about the issue and in a few days they were at my doorstep and I got a quick refund.Try to purchase the products which have a "fullfilled by amazon" mark on them.