Are you by any chance, a residential customer? If so, then you'd need to contact the residential helpdesk: Contact Us
The residential forum is here: BTCare Community Forums
If you are a business customer and use a BT Business Hub, the admin password is easily changed. See this:
How do I set up an admin password on my BT Business Hub?
The Business helpdesk will also be able to assist with setting up a Business Hub: Contact Us
