Vodafone Freebie Texts was an opt-in scheme for Pay as you go customers, but it's no longer available. If you've already opted in, you'll still get extra texts, free for 30 days, when you top up by at least £10. However, if you opt out, you'll not be able to opt back in.
You can save money by buying a Big Value Bundle which will give you an allowance of data, minutes and texts to use over 30 days. They're available online or by calling 2345 free from your Vodafone mobile. Please note: you can’t opt into a Freebie and Big Value Bundle at the same time.