If you haven't signed up for the Next Drive tariff I would suggest doing it by eMail - they checked my eligibility and I got setup within a couple of days, whereas some people posting on here, trying to join by phoning C.S seem to get passed from pillar to post and have to jump through hoops until they achieve success.

Emailed them and they advised I have to switch via the site now. Seemed simple enough. Fingers crossed it all goes smoothly 🤣