It can take up to 24 hours for the port to complete in full, but please turn your handset off, and remove the sim card, leave for 10 minutes. Put the sim back in and restart the device, this should now work. If this doesn’t work – please process a manual roam – Go into settings > data settings > network selection/Carrier services (slightly different depending upon the handset) turn automatic off. The handset will then search for available networks. Select O2/EE/VODAFONE (whichever is applicable to you) this should kickstart service. If it does, restart the device and switch it