The XFX website lists the 750W full modular as "black edition", but a 750W semi-modular as "XXX", so I don't think that there is any problem there.
Regarding the premium number, I looked at a site called saynoto0870, and searched for xfx under "search by company".
It gave a replacement for the premium number (0906 835 4400), namely this (01327 315750)
Edit: Wait, you said that you got the Semi-Modular? That is a tad confusing...