The address given by Helen is the one for their media relations team, that almost certainly only processes enquiries from bona fide journalists.
As Jennyjoan's post suggest, most big organisations don't give out email addresses to the general public. Many use web forms, which serve the same purpose, as messages sent that way end up in someone's inbox anyway. However TalkTalk seem not to have that means of contact either, preferring to use telephone calls or live chat:
https://community.talktalk.co.uk/t5/Articles/Ways-of-contacting-us/ta-p/2230529