Why I don’t have no cellular data

First try:

Manually update your carrier settings on your iPhone or iPad - Apple Support

Then try:

If you see No Service or Searching on your iPhone or iPad - Apple Support

Failing that:

How to back up your iPhone, iPad, and iPod touch - Apple Support

and then:

Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Ameenah2 Said:

"Why I don’t have no cellular data: What going on with my phone"

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Contact your Carrier:

Contact your Carrier as they are the one who provide you with the service of Cellular usage. Ask them about getting around this update issue.

To Check for Updates:

Use a Computer and Ethernet:

Start with attempting an update through use of a computer. If you cannot use Wi-Fi, then use Ethernet.  Go Here: Update your iPhone Using a Computer - User Tip. On the computer, you would connect it through Ethernet, going directly into your router. For a Mac (or PC) that does not have Ethernet, this would be the adapter to use: Belkin USB-C to Gigabit Ethernet Adapter - Apple