Order the sim from the link on your account. Your friend activates the sim by paying £10 airtime credit or goodybag. Your friend will be allocated a giffgaff number but will need to get a pac code from his existing provider and use the links to transfer that number to his giffgaff sim. The £10 credit or goodybag will be transferred too, it will not be lost. It is not a sim swap, this is when you are swapping your giffgaff sim for another giffgaff sim for example if your existing giffgaff sim is damaged or lost or is a different size because of a change of phone. You will get the payback because you are introducing a new customer to giffgaff. Giffgaff will know this because you ordered the sim while logged onto your account.