The default repeat #notifications that come in with SMS texts or iMessages is one setting I wanted to change on my #iPhone. Now only the original message pings on my phone, which is pleasantly less distracting. To enable this:

• Open Settings, then tap Notifications.
• Tap Messages.
• Scroll down and tap Repeat Alerts.
• Select Never so the checkmark appears next to it.

This process works on my iPhone 6s running #iOS 12.1.3.