To change the tracking number and mark as dispatched you have to generate the original prepaid label. Go to View Order Details > Postage > Track Package > dropdown arrow and change the tracking. That has to be done on a desktop browser.
Afterwards if you paid for the original label you can cancel it here:
https://www.ebay.co.uk/claims/simple-delivery/refund/seller
Or if the buyer paid for it it will be refunded to them automatically in 30 days.
But if you don't manage to do the above the payment will be released anyway in 14 days.
