Why is returning items bought online such a mission?

I purchased a trampoline and a swingball set online and it was delivered to my house. I realised then that the items weren't suitable for my children so I went to the nearest PnP store to return it. They accepted the swingball set, but not the trampoline and was told they do not have the item on their system, and I would need to return it to a hypermarket. I then said that the nearest Hypermarket is about an hour's drive from me. They tried to call Hypermarket in Ottery and Brackenfell but there was no answer. The next day, someone called me to find out about my experience when I returned an item that was bought online. I told them about the trampoline issue and was told that they'll look into it and give me feedback but I never heard anything back for over a week. I submitted a query online and the response I received was that they cannot do anything because I received the item more than 7 days ago.

My point is, I do not choose to buy from Pick n Pay supermarket or Hypermarket when I'm buying online - I'm buying what I see on the website. So if I were to return an item, it should be as easy as making the purchase. I'm already losing out because I paid a delivery fee which I don't believe is refunded when an item is returned, and now I still have to drive another hour just to return the item.

Is there no way I can return this item to the nearest PnP store without it being such a mission?