can i update ios using data and not a wifi connection?

No, you need a Wi-Fi connection with a 6S (and not a personal hotspot, either). An iPhone 12 or 13 series can update using 5G cellular data, but not any other models.

The alternative is to update using your computer as described in the Related Article at the top of this page.

Scroll to the top of this page and click on the blue text under the Related Article heading. Or click here→Update your iPhone, iPad, or iPod touch, which is the same link.

Then you can’t update your phone. Updating using your computer does not require formatting your phone if you follow the instructions in the related article.