Try this.... Will temporarily work til you reboot your phone. But I no longer have an older device to test further.
Try this it won't remove it but at least mute it til you reboot.
Go into settings Apps Click on the 3 dots in the upper right hand corner Choose Show system apps Go all the way down to Sprint OMADM and Sprint OMADM Phon.. FORCE STOP . . . If you've found my post to be helpful, please like the post. If my response resolved your issue, please press the "✓ Accept as Solution" button by pressing the three dots on the comment.