Talktalk customer service

I have been having an issue with talktalk, for over a month now.
I am now at a complete loss as to what to do next....

I currently use talktalk for my emails only (I used to use them for broadband back in the Tiscali days). While I switched to another internet provider, I kept my email account, for convenience. I have had the account for over 10 years.
At the beginning of last month, my inbox vanished. Every single email I had received was gone. Other folders (drafts, sent, etc.) untouched.
I complained immediately via their online support, and after some hours of discussion, was told, there was an issue, and an email specialist would get back to me within 5 days. 5 days past, and I tried to chase it. I was told, eventually that as the 5 days has passed, i should ring a given number that would put me through to said specialists. The number was in fact the basic call centre. After around 1 1/2 hours of bouncing from department to department (even accounts!), I as told someone would call back.
You can probably guess, nothing has happened. I tried to raise a complaint. There seems to be two ways of raising a complaint:- vai email, or a paid for phone number!!
I have emailed them 14 times now. Occasionally they reply, asking for account details, such as my address, postcode, email account and, once or twice, talktalk account number. I have provided all on multiple occasions, with the exception of the talktalk account (I don't have it anymore).
The last email I has said "Unfortunately, we are unable to act upon your query without first confirming your details with you. This is a legal requirement as per the Data Protection Act of 1998. "
This seems to be a stock answer, meaning "we can't be bothered", as this was a reply to my email, with said details.
I can now confirm Talktalk have the worst customer service I have come across.