I have just upgraded my shared SIM contract with a new phone but have kept my old Harrier Tab. My Harrier works fine on WiFi but fails to work on mobile data and keeps giving the message 'sign in to network ee'. When I click on it I am directed to the EE website and offered a data add-on for an additional cost. When logging into my account my shared SIM has 12GB data left and both devices are listed as expected. Please help!