Fitguru and Offerguru are 'Payforit' scams operated by a company called Taptronic and using shortcode 64055.
These companies use vulnerabilities of the 'Payforit' system to obtain consumers numbers and sign them up to bogus subscriptions. Simply closing an innocent looking popup can pass your number to these scammers.
GiffGaff appear to have a policy of not helping members affected by these scams, so you will have to take action yourself to stop the charges and obtain a refund.
Sending a STOP ALL text to 64055 should stop further charges. You can then call them on 03302232719 (Offerguru) and 0330 223 1099(Fitguru) to insist on FULL refund
Fitguru are well known scammers. Take a look at their reviews on Trustpilot.
It is legally negligent and morally reprehensible for GiffGaff to allow this company to continue to plunder their memebers funds.
'Payforit' subscriptions are not strictly premium texts, although they are shown as such on your GiffGaff usage statement. 'Payforit' charges are applied directly to your account by a 'third party' which has acquired your phone number. GiffGaff make no check that you have consented to these charges, and refuse to allow you to bar them.
You need to be aware that GiffGaff leak your phone number to third parties when you access the internet using mobile data, and this is probably how your number was acquired in order to make these charges. The system which does this is called 'Payforit'.
Comprehensive and independent information and advice on dealing with these scams is on the payforitsucks website. This website won't blame you for being scammed and provides constructive advice about forcing the scammers to refund. Support is also available if you encounter difficulties. Google "payforitsucks" or follow the link to the faq in my signature. The website contains detailed advice on the steps you need to take to stop further charges, obtain a refund and protect yourself from these scams in the future.
I hope you manage to resolve this matter. These scams are a disgrace to the mobile communications industry and GiffGaff should be doing more to assist affected members and to protect members from these scams.
Just an update on my son being scammed by Fitguru. Giffgaff weren't interested ... other than telling me to change his account settings to block such numbers.
I did indeed ring the number, debated strongly with a foreign lady who said she'd text my son a code within 10 working days and he should take that to any Post Office for a refund. The text took a lot longer than 10 days and I was about to ring them again when it arrived.
Took him to PO yesterday and they didn indeed punch in the code number in that text and promptly gave him £3 cash. So it does work if you argue your case with them and insist on a refund.