If you mean the password details for the broadband that's stored in the router, you would need to call the tech support desk and confirm the security question 1st. If you mean the password that's used to restrict access to the router GUI (and you're talking about the 2700HGV), then this password is set by yourself and BT don't have access to it. You would need to go through the forgotten password options to get regain access again.
