Get over it.
This is the same ISP that promised "no mid-contract price rises", and then went on to introduce mid-contract price rises:
https://www.ispreview.co.uk/index.php/2021/07/asa-pr...
Even if you could point to a specific advertisement which made the claim you are referring to (note: an advertisement, not a public statement by Dido Harding), the ASA isn't going to do anything about an advert three years old. Company policies and offers *do* change over time.
Not that the ASA can do anything anyway, apart from issue a public warning and instruction not to run the advert in its same form again. They cannot instruct Talktalk to offer you a refund or to release you from your contract.
If you like Talktalk's service and pricing, then stick with them. If you don't like it, then choose a different provider. However, remember that you got a really good deal - one no other provider is likely to match - so if you walk, you will pay.