If you are keeping your current handset then continue to use it until you lose the service from your existing network. Then switch off the handset, remove the old SIM card and replace it with the new one we have provided.
If you are changing handsets, then when the existing SIM card loses service you should put our SIM card into your new phone, and switch it on.
Service can sometimes be lost for around 3 hours on the porting day. This usually happens some time between 11am and 3pm and always between 9am and 5pm at the latest.