Welcome to our Community and thanks so much for your first post; we are sorry about any confusion caused via these text messages. Yes - we are currently contacting our customers to advise that a new SIM maybe required due to migrating our services.
We would have already tried contacting via letter or email if possible - did the text message advise to reply with your address/postcode information so the new SIM could be posted?
We've been unable to locate your account from your forum information so have been unable to check your account for you. If you're still concerned, please do pop back and let us know or you can call us at anytime from your mobile on 789 or pop us a text on 07533016422 if you wish