scroll down to ‘Reset’
Select ‘Reset Network Settings’
enter you pin and let it rest.
I always recommend that once this is done, restart the device, remove the sim card, wait a minute and re-enter the sim card. Once he phone accepts the sim it should download new carrier settings and apply them to the phone. Be mindful of this when you enter the sim, a message should appear asking if you want to install the new carrier settings make sure you accept them .