When you enable Do Not Disturb mode on the iPhone, it will silence all the contacts from calling you. But, if the same person tries to call you three minutes later, then the call will bypass the DND mode on the device and it will ring your iPhone. To combat that, you should disable the repeated call settings.
When you call a dead phone does it ring?
Answer: A: With a dead battery it should not ring but it should go to voicemail directly.