I can update 15.7 on my phone.every time I am getting error.want let me finish.

Hey mmedatia,

We'll be happy to help out with updating your iPhone.

Take a look at the steps here as they have some of the best solutions to resolve update issues: If your iPhone, iPad or iPod touch won’t update - Apple Support. If you're still having trouble updating, then try updating using a computer. Take a look under the section "Update your device using your computer" here: Update your iPhone, iPad, or iPod touch

Let us know how that works out for you. Cheers!