How can I cancel an order that I have paid for as it wasn’t what I though it was

[kopenhagen5]

You can't, only the seller can.

The seller may have sent it already and they have already paid fees.

Contact the seller to see if something can be done otherwise you might just need to resell it yourself.

[enigmabear]

Was there something wrong with the item description? 

[papermoon.lady]

I think you should contact the seller as soon as possible if you wish to cancel (before they send the item). Some sellers are quite accommodating.