Go to the Talktalk Community forum.
http://community.talktalk.co.uk/Register to join, or login with your current details, I can't remember if you have an account automatically.
Make sure your profile pageon there is then up to date, phone number etc.
Make a new post in, "Help with your TalkTalk service/Unlimited Broadband"
Title it "Possible scammers phoning me", or something like that.
It's a public forum for all TT customers. You 'will' get a reply in the next few days from one of the team.
The forum is also a good place to report faults if you have problems with your broadband but can still access it from somewhere/something else