If you’ve been turned down for a full refund, it’s probably time to send a letter before action to try to recover your money. This is an essential first step in the Small Claims procedure.
Effectively you quantify your loss and explain why the organisation you are sending your letter to are liable for your loss. You should try to anticipate the likely arguments that the organisation will use to counter your claim and answer them.
The simplest letter is one sent to the company that operated the “service” which took your money. There is no dispute that they received your money, and you maintain it was taken without consent. Unless they can prove you consented to the charges, they need to refund in full.
A template Letter is provided here: Letter before Action (Service provider)
If the company operating the “service” which took your money doesn’t have a UK presence, or seems unlikely to pay your claim, you will need to pursue the Level 1 provider instead. They will probably try to argue that they were only an intermediary, but I think it likely that a court will hold them liable if you are unable to take action due to the “third party” company being in a foreign jurisdiction.
An template for such a letter before action is here: Letter before Action (Level 1 provider)
Sometimes, it might be better to pursue your network for your losses. This is potentially more difficult as you will need to establish negligence on their part. If you are dealing with a “service” about which you can find many complaints (just try googling it!) then you can argue that your network should have been well aware that there was a problem with this company and were negligent in not doing anything about it. Unless your network has properly investigated your case you can also refer to the Payforit Code of Practice and say that your network has not met it’s obligations under this code. https://payforitsucks.co.uk/mobile-operators-code-of-practice-for-the-management-and-operation-of-pfi-2/
A template letter before action is here: https://payforitsucks.co.uk/letter-before-action-network/