I am sorry to read that you have received an unsolicited premium rate text message, which has deducted £ 4.50 airtime credit from your giffgaff account. Unfortunately this is an issue that is affecting all mobile network operators, not just giffgaff.
For a giffgaff guide on the do's and don'ts regarding Premium text charges @morecakeplease, please click this link https://community.giffgaff.com/t5/Tips-Guides/Premium-text-charges-do-s-And-don-t-s/m-p/18597940/highlight/true#M145989
Giffgaff advise that you text STOP to the shortcode message to prevent future charges (i.e. STOP to 83463) HELP 03300535843. You'll need airtime credit to text a shortcode number https://giffgaff.com/top-up.
In addition to the above, please click the following link to be directed to Ofcom appointed website of the Phone-Paid Services Authority. This will give you guidance on what to do when you receive unexpected phone charges. http://psauthority.org.uk/for-consumers/unexpected-phone-charge
The Phone-Paid Services Authority regulate Controlled Premium Rate Services. The Phone-paid Services Authority regulates all premium rate service providers in the UK who have to abide by a Code of Practice. The Phone-paid Services Authority use this Code to make sure premium rate pricing, advertising and content is clear, honest and appropriate.
The Code covers all controlled premium rate call and text services. As well as 090, 091, 098 and 118 numbers it therefore also covers services on 087 numbers and usage of 070 Personal Numbers and calls and texts to mobile shortcodes.
The Phone-paid Services Authority is independent and free. They investigate all complaints about Controlled Premium Rate Services. They can fine companies, shut down services and prevent people from running similar services if they breach the Code.
The Phone-paid Services Authority can be contacted via:
Their website: psauthority.org.uk
The helpline on: 0800 500 212
Letter to: Phone-paid Services Authority, Freepost, WC5468, London SE1 2BR
Textlink: 020 7407 3431 (for customers who are hard of hearing)
Give them all the information you can about the service you want to report – like the number or five-digit shortcode, where you saw the service advertised and what it said.
In the meantime, it is worth mentioning that Premium Rate services like this can only take money from any airtime credit (standard Pay-As-You-Go top-up) balance you have, so, it may be an idea to purchase a goodybag bundle instead, at least until you get this sorted. https://giffgaff.com/sim-only-plans
You can also convert airtime credit into a goodybag too. Please click the link below for a full step-by-step guide on how to purchase a goodybag from existing airtime credit.