angiekeith114 Thank you for contacting the giffgaff Community.
You need to send STOP to the 5 digit number mentioned in the text
You need 10p credit to send the STOP message, but in their original text message there will be a customer services number which you can call from your goodybag minutes, call them inform them you never subscribed, don't wish to be subscribed and to remove your Number from their Database.
It is important that you do send the STOP text or call them so that you get them to unsubscribe you, if you don't then you may well be subject to future charges to receive their texts!
Simply blocking the number will not stop the texts or charges as they are charged at network level, blocking simply stops them appearing on your phone but you will still be charged
You can enter the 5 digit number here http://psauthority.org.uk/about-us/number-checker to find alternative contact methods for them!