It would appear that, at last, EE are doing something about these subscription scams.
The links below relate to changes being required by EE for subscription services using Payforit. Essentially EE are now requiring two step authentication for all subscription services using Payforit. This means it will no longer be possible to become signed up to these services just by clicking a link.
https://blog.impulsepay.com/post/170580247572/ee-flow-changes-15th-february-2018
https://clients.txtnation.com/hc/en-us/articles/360000656991-UK-Changes-to-PFI-payment-flow-on-EE
What isn’t clear is whether EE will apply these requirements to it’s ‘own portal’ services (which don’t use Payforit).
At least one of the networks appears to be taking some action to stop these scams.