To update my iPhone X system Using my cellular data

You can't.

If you don't have Wi-Fi at home, head on down to the coffee place or the bookstore and use the Wi-Fi there. If you have an Apple Store nearby, you can use the Wi-Fi there as well.

jusu256 wrote:

But can I update it without WiFi using my cellular data?

I'm not sure how many times you need to hear the same answer, but NO, you cannot update an iPhone X using cellular data. You MUST have access to Wifi and no matter how many times you ask the same question, the answer will be the same.

No. Stop asking the same question. The answer will not change.

Contact Apple Support.

Support

Already answered. Asking the same question again and hoping for a different answer won't change things.