It is a scam. As long as you never entered any information and as long as the link did not cause anything to be downloaded onto your device you should be ok.
To be on the safe side run a full virus scan and it may be best if you keep an eye on things such as online banking if you use that. You should also consider changing your email password.
In future be aware that BT will never ask you to update your account. You should not click on any links in unsolicited emails especially if they want you to verify anything such as email accounts or bank accounts.
