T-Mobile Unlimited Web, Text, 100 minutes talk - does it require new activation?

I've been checking out this month to month plan for a long time but I just noticed that in small print (on the web) it says "New activations only. Available exclusively in-store at Walmart, on Walmart.com, and T-Mobile.com.".

Has anyone gone from a contract on T-Mobile and then switched over to this plan? Just trying to figure out how I can go about getting my girlfriend on this plan while still keeping the current number that she has associated with T-Mobile. I think getting a new number/activation w/ a new number is completely a non starter with her.