A hard reset is basically the resetting of the settings and applications on your device. You would typically do these to assist with minor issues such as calls dropping or signal intermittency.
To complete a hard reset you will need to power off your device, due to multiple devices being out there if you struggle please contact us at [email protected] or 0333 202 5000 option 1 for Customer Services then option 1 for Mobiles and a member of the team will be happy to assist., once we know your device we can advise the steps you are to take.