If you get your o2 bill and it is higher than expected and on checking the bill in myo2 you find have either have a premium rate charge or a charge to mobile value on your bill, then you may have fallen for a scam on the internet or actually used one of the services.
O2 has provided a short video (see below) explaining about premium SMS numbers and how to avoid "bill shock":
O2 are not the ones that regulate this type of common issue but the regulator Phone-paid Services Authority. In this self-help guide, I hope to point you in the correct direction to hopefully get your money back from the scammers.
Facebook and other social media platforms are where these scams come from and by being more vigilant on there should also help you in not getting these in future.
O2 can only apply a block on your account for outgoing premium rate services (Confirmed)