Unhappy with wrong item in correct package.

I have ordered a queen size mattress protector from Takealot and received the item. The item on the outside of the package read queen size which was correct.

Then I opened the parcel thinking I will find the correct item inside. I saw the label on the item was for a double bed which was not what I ordered. I have send several emails which is stating that the return requested was declined because I opened the package which is fair in some cases.

I have send also a couple of emails stating that it is now my fault that Takealot put the wrong item in the package or labeled the package incorrectly. How can you decline my return and also don't refund my money if this is not a mistake from my side. How do you know that the correct item is in the parcel if you don't open it?

You now have the item and the money I paid.

All I want is a refund into my bank account.

Can someone please make an effort to fix the error - Cell: ***