Don't contact BT, you have no contract with them and they have no responsibility towards you.
Firstly telephone Talk Talk. Make a note of the time, date and the name of the person you speak to.
If needs be, follow this up with email, giving the details of your phone call and the full nature of your complaint.
If you are still not happy, write to them by recorded letter, giving the details of your complaint; the initial phone call and subsequent emails.
All the contact details are here:
http://help.talktalk....i-make-a-complaint%3F
If you are still unhappy contact Ofcom.