How to turn off repeat notification when phone is on do not disturb

[Android Central Question]

Hello. I work as a police station duty solicitor so I regularly put my phone on DND so it just allows calls through. Despite this, I am always woken up by my phone vibrating every minute or so even though repeat notifications are turned off on my Samsung A5 2017 model. Please please someone help me get to the bottom of this is is driving me mental!! Thank you in advance!!