Back in May I recommended a friend to BT and she then signed up. We both got emails promising us £50 Amazon gift vouchers, but neither of us have received them. I hope that a moderator on the site will read this and will act on it.
have you tried phoning CS 03301234150 and see if the can help
or try billing https://www.bt.com/help/contact-bt/account-and-billing/broadband