If you were still in contract, you might be offered a "free upgrade", which would mean that you'd continue to pay the same price as before till the end of the contract, @tony362.
As you are out of contract, the only way to reduce the price is to take up the offer and commit to however many months is offered at the lower price. (Prices vary by duration of contract / location etc). So a new contract.
So you really need to phone or use Chat to clarify the exact deal, or phone to confirm cancellation of your service, if you are moving elsewhere. Switches to FTTC with another Openreach provider can be done by contacting the new company who take over your line (ask to keep your phone number), but for every other sort of switch you are responsible for telling Talktalk.
Or if you can also simply stick with Talktalk on FTTC if it is still available in your area - again, check prices which vary with duration.
Whatever you do, staff can't fix this up or set up the contract / cancellation for you.
For cancellation you must phone 03451 720088.
For taking up any offer, use Chat or phone. Opening hours are detailed at the bottom of this page:
https://community.talktalk.co.uk/t5/Articles/How-to-contact-TalkTalk-Broadband/ta-p/2230529
Prices are listed near the bottom of Talktalk's own webpages that publicise products. The small print section shows all the separate products and tariffs.
Gliwmaeden2, a fellow customer.
