Does that mean that things like returncall will stop working on Voda?
My understanding is that Vodafone has or will block all premium texts.
So it looks like the end is in sight for such services.
My best guess, therefore, is that existing credit will continue to be available to use until it is all gone. However returncall will no longer be able to send you £5 topup SMS's to refresh your account.
( Given the way in which they have increased their prices after drawing in a lot of subscriptions, that may not be such a bad thing though! )