You must make sure that you are accurate and truthful when informing the seller of the defect or damage affecting the product. If the seller returns the money to you, and does not ask you to return the item, there is nothing wrong with you making use of it, because it is an item that the owner no longer wants.

Dropshipping is halal if you turn it into profit-sharing or if you act as an agent in return for a fee.

Buying an item online may be done in several ways, in some of which it is valid to delay payment until the time of delivery, and in others that is not valid. See more details in the long answer.