You said that it was an unfair demand. I am sorry if I let you angry. However, it costs some amount of money to send it back, and, in addition, discount of 5 pound is to little. I need 16 pound of discount at the least. Thank you.
It would seem that you feel I am making an unfair claim. I apologize for making you feel that way. However, it costs money for me to return the item, so I think a £5 transaction is too low. At the very least it should be £16. Sincerely,
すいません、間違えました。transactionではなくdiscountですね。