You will need to contact the website, business, or person that you sent bitcoin to and provide them with your Transaction ID, which is like a receipt or proof of payment. You will need let them know that you sent bitcoin to them, and that you would like to have the transaction refunded. The Transaction ID can be found by tapping on the wallet that the transaction was sent out of. You will then need to tap on the transaction that you would like refunded, and open the "Advanced Transaction Data" information. At the transaction data screen, you will see that the Transaction ID is displayed, along with other information, including the number of confirmations that the transaction has received. The transaction data link is the relevant link to send to the other party, which shows proof that payment was made.
Once a Bitcoin or other cryptocurrency transaction has been sent, the transaction is irreversible and cannot be cancelled. This is the way cryptocurrencies are designed and applies not just to Edge, but to all other wallets and services as well.