You'll need to ask Chat or phone support on 03451 720088 to do this for you, @JALNA-ROBERT, if it's not working for you in My Account.
Check their opening hours here:
https://community.talktalk.co.uk/t5/Articles/How-to-contact-TalkTalk-Broadband/ta-p/2230529
It's just a boost that needs to be added to your package, not an upgrade. Remember that you can't call for more than an hour except to Talktalk customers [3 hrs to Talktalk customers] so you need to redial when approaching 60 minutes to avoid incurring charges. And they only cover ordinary landline 01, 02 and 03 and usual mobile numbers, not 0870 etc.
Gliwmaeden2, a fellow customer.
