I have 2 old ee iPhones which I want to give my children to use. Will BT Sim only cards work in them?
It may depend on if the old EE handsets are locked to EE.
Have you tried a BT Mobile SIM or another network SIM in them?
Mobiles locked to EE should work with no problem with a BT SIM card.
Much older phones will show the network as one2one.