The router will have come with a package that's now out of its minimum term contract.
Use the main Talktalk website to check whether full fibre is available in your area, and check also in "offers & upgrades" in My Account, @Samaneh-.
You can also speak to Talktalk directly on 03451 720088 or Chat. Check opening hours near the bottom of this link:
https://community.talktalk.co.uk/t5/Articles/How-to-contact-TalkTalk-Broadband/ta-p/2230529
Renewing your contract anyway should bring the price down.
To upgrade:
Some fibre150 services can use the Hub2 - if you want to keep the use of your phone number, you must ask to have VOIP with your order - it can't be added later.
If they send an Eero rather than the Hub2, you'll also need them to send you a digital voice adapter.
If the router you already have has a phone slot in the back, among the other slots, you already have a Hub2 and won't necessarily need a new one.
Gliwmaeden2, a fellow customer.
