No return policy

Assalamu alaikum. When I sell product via online the I give the images of product along with the main description of the product. I mainly don’t have any return policy. In description, I write that small spot or small thread knot will not be granted as defect. (and sometimes I try to give example with the image). And declare that, after confirming order it can not be cancelled. Though sometimes some customers ask to book/send a product and then after some days they ask me to cancel it. Which causes issues to my business. In such cases, sometimes I convey them the message like: such cancellation is a loss for me. Though I cancel their order and also decide myself that I will not sell anything to them in future.

Recently one customer wanted to exchange a product which she bought 5/6 months ago because she liked the other product. Though later I discussed with her that it is not possible for me. So, after that, Recently in some post I also write that, with out defect parcel can not be returned. And customer has to check the courier in front of courier delivery boy. After receiving the product it can not be returned. It is very much well known that parcel should be checked in front of the courier delivery guy and if any defect found (in post description I declare the characteristics which are NOT supposed to be granted as defect) then it should be returned to him. I am also planning to add in the policy that "if any defect found in the product then return it to the courier delivery boy. Parcel can not be returned/exchanged once courier boy has left the place. " something like this.
Is such return policy ok?