1pMobile and all other telecom companies have a legal obligation to allow these texts to be sent to your phone, we cannot block them and we cannot refund your money, the money refund would need to come from the company that originated the text message, if you can prove you didn't sign up for the texts, they also must stop sending them if requested.
Some rogue apps will sign you up for these sort of texts or sometimes a website hides the fact in their small print when they ask you for the phone number.
It is also possible said the rogue company claim people clicked on an advertising link that automatically subscribes you to such a service.
To complain about these text messages and charges please refer to the Pre-paid Services Authority (PSA): https://psauthority.org.uk/for-consumers/unexpected-phone-charge
There is also a handy article here at the Citizens Advice website: https://www.citizensadvice.org.uk/consumer/phone-internet-downloads-or-tv/complain-about-a-premium-rate-phone-charge-or-text-message/