I’ve been whiling away the past hour, researching this one too. Expected myself to conclude there’s more to it but, although seemingly ridiculous, I think it might be possible.
If a user subscribes to premium texts it should need an auditable action on their part and imho the onus should be on the mobile operator to maintain proof that a subscription is genuine, and of course, to refund the user in case of fraud.
In my trawls, I found this article from the Consumers Association, which has also ruffled my feathers (my highlighting)
https://www.which.co.uk/consumer-rights/advice/im-being-charged-for-unwanted-premium-rate-text-messagesBe wary sharing your phone number
Unfortunately a lot of people subscribe to premium rate text (SMS) messages by mistake – for example, by failing to tick or untick a box on a website or replying to a message.
This means you should be even more careful when entering competitions or registering for a service.
Think of your phone like your credit card - if you give out your number, you could be charged.
Unless you're really confident you know how a website will use your number, don’t enter it online.
Sounds like victim-blaming to me. Yes, people should be wary of disclosing mobile phone numbers for reasons of privacy, and they have only themselves to blame for that lack of privacy. But to suggest that loss of money from the account is also a reasonable expectation from disclosing a phone number is plain ridiculous in my eyes.