How to fix 10.3.2 battery drain issue
Step1. Download ios - 10.3.1
Step2. Connect your iphone to itunes and hold down the shift key and hit the restore button at the same time. This will open a folder box. Select the ios 10.3.1 that you downloaded. (If prompted do not do a backup, will be useless. )
Step3. When prompted to restore from a backup once the phone gets done with the upgrade choose setup as a new phone. You will need to install all of your apps and resetup your settings from scratch. (Its a pain in the *** but it is necessary)
Step4. If prompted to do a carrier update - DO NOT INSTALL CARRIER UPDATE. Hit later when asked. It will prompt occasionally , just continue to hit later.
Your phone will now get its battery to last all day. The issue is not 10.3.2 but the carrier update, the issue is the carrier update is embedded in the 10.3.2 update which is causing your radio to always run at full power. After some research it appears to only impacting ATT Iphone 7 / 7+ / 6s and 6S+. I have had apple replace the phone twice and each time same results with 10.3.2