How to Keep Others from Replying to Messages on Your iOS 10 Lock Screen
If you own an iPhone 6s or 6s Plus, or will be getting an iPhone 7 or 7 Plus, the new iOS 10 lets you 3D Touch some lock screen notifications to respond to a message without even unlocking your phone.
Step 1. Head to the Touch ID & Passcode menu in Settings.
Step 2. From here, enter your passcode, then scroll down and disable the “Reply with Message” option.
From now on, nobody will be able to respond to notifications on your lock screen.