Please update my Apple iphone

To update to the maximum of iOS 12.5.7, please see: Update your iPhone, iPad, or iPod touch - Apple Support

And: If your iPhone, iPad, or iPod touch won't update - Apple Support

If the above Apple articles do not help, please post back with relevant information. 

Please follow the instructions posted above, or provide details as to what happens when you attempt to update. If your phone is running iOS 12.5.7, it can not be updated further.