Unsatisfactory

I ordered pizza on the app and few minutes later I got a call saying they could not deliver as it was raining but I had paid on the app, the cashier told me there is nothing they can do I must request for reversal on the payment when I asked why they didn't update on the app she said they can't. So now I said I can't come and collect due to personal reasons. Let's cancel the order . To my surprise it said the pizza has been delivered and it wasn't, now my problem is how can I make a reversal of something that says delivered.