Update
Can you update your phone during the day with cellular data
iPhone 6s, iOS 12
Hi abena,
Click on the link below for full instructions about how to update with wi-fi or 5G (if using 5g then see: Use 5G with your iPhone Use 5G with your iPhone - Apple Support ), or using a computer if you cannot use wi-fi or have storage issues.
Update your iPhone, iPad, or iPod touch wirelessly. Click here --> Update your iPhone or iPad - Apple Support