Sorry to hear of your woes.
It is a fact of life that when you speak to 'BT' you are speaking to a call centre (in India?). The agent will be taking calls for several companies, and logs on to the appropriate database.
These will be programmed with the response to be given to a question, the agent cannot override these.
Can I suggest you read the information in the phone book under Customer Services ('If you still have a problem' section) which has several phone numbers to try. Also the Code of Practice has, amongst other things, a HomeMovers hotline on 0800 800 123. You may get more sense out of them.
Lastly, consider putting your thoughts in writing to BT. Unlike phone calls, a letter will quickly find its way to the right department and someone who can help.