In future, if you post to Discussion > Buying you will receive a quicker response.
eBay works best step-by-step, so if you request a cancellation and it is denied, the next step is to wait for delivery of the unwanted item. When you have the item, then you can open a Return request (otherwise you don't have an Item to return). I can understand wanting to sort this as quickly as possible, but it's best to be a bit more patient - to give the Seller, eBay, or ourselves time to understand and respond to the situation. Don't worry, we've all done it. Sometimes eBay has a steep learning curve. I hope found a use for the 2nd item, or resold it on eBay to someone else who can use it.