Can you please try turning off your phone again but this time please remove your SIM card for 10 - 15 minutes. Then go ahead and re-install your SIM and turn your phone back on. This will force a network update to your device and hopefully, if it has been applied correctly, your service should function correctly.
You can also check to ensure that you have 4G or LTE enabled on your device by following these steps:
On the homescreen, swipe up for the Apps menu.
Tap Mobile networks.
Tap Network mode.
If you want to use 4G, make sure LTE/3G/2G (auto connect) is enabled. If you just want to connect to our 3G network, choose 3G/2G (auto connect) or 3G only.
If none of the above works, please get in touch with Boost Support on 125 8881 (8am-9pm, 7 days) or via Live Chat (24hrs, 7 days) and we will happily assist you further in getting your service up and running.