hgovi30 Hi there. That’s right… giffgaff SIM cards will only work in unlocked phones, or phones locked to the O2 network (as giffgaff runs on the O2 network). If your phone is requesting a service provider (SP) code, network SIM lock code, SIM network PUK, SIM network unlock PIN, access control code or a network unlock code (NUC) when a giffgaff SIM card is inserted, this would suggest that your phone is locked to another network.
If your phone was used with Tesco Mobile, please take a look at Tesco Mobile’s phone unlock page for unlocking information (please have your phones IMEI number to hand).
If your phone is locked to another network, you’ll need to get an unlock code from the network in question, so that you can use it on giffgaff.
Want more information about this? That’s where Unlockapedia can help, here you can find free, impartial advice to help you unlock your phone.