My Motorola Moto E (4th Gen) is letting calls through in Do Not Disturb Priority Only mode

[AC Question]

For some reason, calls are getting through when I am in Priority Only mode and listening to the IHeart Radio app on my bluetooth speaker at work. I have Priority Only set to not allow calls. I don't know if it would matter but I have T-Mobile prepaid service. I am not having any luck trying to figure this out with the Google. Any help will be greatly appreciated.