Lock screen app uninstalled but still somehow on my phone

[AC Question]

So today I downloaded this lock screen app called 'Next' lock screen app. I decided to uninstall it. It uninstalled fine but it is still playing noises on my phone occasionally which is really annoying. I've tried re&un-installing and downloading androidassistant to look for any files left behind but with no luck

If anybody could help me with this I would really really appreciate it

Phone is a Nexus 5

 

[Guytronic]

Looks like in permissions it was enabled to modify system settings.
It may need to be turned off under "security" if it has been allowed to integrate deep in the system.
Certain apps won't uninstall unless they are disallowed all the permissions required.