We had their phone service. My partner needed ADSL to allow remote working, so we enquired about their advertised "broadband for £6" or something like that. We were told it didn't apply to us, it would be £20-odd (I can't remember the exact amounts).
Then a letter arrived, welcoming us to TalkTalk broadband! The person we'd spoken to, to whom we had *firmly* said "no thanks", had signed us up. We cancelled this, of course. Then, a short while later, we got another welcome letter- we'd been signed up again!
As soon as we were out of contract, we cancelled their service and put them on our "do not use, ever" list.