Hi, which phone do you have?
some android phones have a setting that prevents you texting shortcode numbers
You need to locate the premium text setting and click to
Incidentally, most charity 5 digit numbers starting 7 (including the comic relief ones)
Are free rated on giffgaff
So if you add a £10 or £20 top up
You can send the text with the key word included
And donate the full ammount