How can I update

Hello.

To turn on cellular service, go to

Settings > Cellular > Cellular Data ON

If it is already on, move to a different location, maybe you will get a better signal.

If you can’t get a cell service signal, contact your carrier.

Marking your own post as Solved may prevent others from trying to help because they think you have fixed your problem.

See if anything here helps.

iPhone - Carrier settings on your iPhone or iPad - Update