I have just bought an iPhone 6 and when I insert the sim it says no service, What should I do?

My mum is with the same network and she has service. I have already restarted it and updated the software to iOS 8.4

1. Check your coverage area to make sure you're in an area with cellular network coverage.
If you can't connect to a cellular network, make sure cellular data is on in Settings > Cellular.
If you're traveling internationally, make sure your device is set up for data roaming. Go to Settings > Cellular > Data Roaming.
2.Restart your iPhone or iPad.
Check for a Carrier Settings Update.
Remove the SIM card then reinsert it. If the SIM card is damaged, worn, or bent, or doesn't fit in the SIM tray, contact your carrier.
Try another location. If possible, see if other devices are able to connect to your carrier's network in that location.
Contact your carrier to:
Verify that your account is active and in good standing.
Make sure there are no outages in your area.
Check that your device is not blocked from receiving cellular services and set up with the right data plan.
Update your iPhone or iPad to the latest version of iOS.
If you still can't connect to a cellular network, and have confirmed with your carrier that there isn't an issue with your account or network, try restoring your device.

Contact apple, their support is worth more than asking a question on here