I'm not sure what you mean, your sentence isn't overly precise.
Do you mean that you want individual ringtones for your contacts?
If so then I don't know how EE, not the phone it self, would do this and I've never heard of giffgaff doing this.
You don't specify what phone you have but if it's an iPhone, as far as I know, you can't. They're trouble as it is with setting a general ringtone and I've never seen or heard about individual ringtones.