I suggest you read this helpful advice from the main tbb site http://www.thinkbroadband.com/guide/resolving-a-broa...
and this from the Ofcom site http://consumers.ofcom.org.uk/tell-us/telecoms/
Don't waste any more time making phone calls!
Write a letter to:-
Nigel Pearson,Senior Director,Customer Services,
11 Evesham Street,
Set out the facts,with dates where you can.Be polite and ask for his personal intervention.
Send the letter by recorded delivery (or whatever The Post Office call it now) and send a copy to:-
2a Southwark Bridge Road
note at the end of the letter Copy to Ofcom.for information only.
It will do no harm to email a copy of your letter to TalkTalk if you have their address.
Good luck and let us know what happens.